OPINION OF THE COURT
SEITZ, Chief Judge.
General Teamster Local 326 (the Union) appeals from a final judgment entered in favor of Delaware Coca-Cola Bottling Co. (the Employer) awarding damages under § 301 of the Labor Management Relations Act, 29 U.S.C. § 185 (1976), for a strike at the Employer’s Wilmington, Delaware, plant.
I.
The Employer is engaged in the business of producing and selling soft drinks. In November of 1975, the Union was certified as the collective bargaining representative for the production and maintenance employees and the drivers at the Employer’s Wilmington plant. Following certification, the Union and the Employer commenced negotiating a contract.
In the spring of 1976, the Union and the Employer reached an agreement as to the production and maintenance employees and signed a collective bargaining agreement that went into effect on June 1, 1976, and that was to remain in effect until 1979. Articles 14 and 15 of the contract established grievance and arbitration procedures. Section 1 of Article 14 defined a grievance as “a dispute or complaint arising between the parties hereto under or out of this Agreement, or the interpretation, application, performance, termination, or any alleged breach thereof.” Any such grievance would be processed through a three-step procedure, which, if no resolution was reached, would lead to arbitration under Article 15.
Article 16, which is the subject of the dispute here, is a no-strike clause. It provides:
Section 1. The Union will not cause nor will any member of the bargaining unit take part in any strike, sit-down, stay-in, slow down in any operation of the Company or any curtailment of work or restriction of service or interference with the operation of the Company or any picketing or patrolling during the term of this Agreement.
Section 2. The Company shall have the right to discipline up to and including [1184]*1184discharge of any employee who instigates or gives leadership to, or participates in any strike or work slow-down or curtailment of work during the term of this Agreement. Any disciplinary action meted out or imposed by the Company hereunder shall be subject to the grievance procedure of this Agreement, including arbitration.
Section 3. The provisions of this Article, other than as mentioned above, shall not be subject to grievance or arbitration, for the purpose of assessing damages or securing specific performance, or any other matter, such matters of law being determinable and enforceable in the courts.
After the signing of the contract, negotiations over the drivers continued for approximately one month. These negotiations stopped on July 9, 1976, because the Employer had decided to engage Countrywide Personnel to supply it with drivers. The Employer transferred all its drivers to Countrywide, and the Union negotiated a collective bargaining agreement with Countrywide.
On March 22, 1977, the Employer terminated its relationship with Countrywide, and the drivers once again became employees of the Employer. The next day, the president of the local called a one-day strike of both the production and maintenance employees and the drivers. The Employer and the Union then once again began negotiations concerning a collective bargaining agreement for the drivers.
On July 19, 1977, no agreement having been reached, the drivers set up a picket line at the plant. Although the production and maintenance employees reported for work that morning, they refused to cross the picket line. This occurred each day for nine days until on the afternoon of the 27th the Union ordered the production and maintenance employees to return to work. The drivers continued to picket until August 12, when they returned to work.
The Employer filed this suit in district court under § 301 of the National Labor Relations Act claiming that the nine-day work stoppage by the production and maintenance employees violated the no-strike clause in the 1976 collective bargaining agreement. After a non-jury trial, the court concluded that the work stoppage was a sympathy strike and that the no-strike clause waived the production and maintenance employees’ right to sympathy strike. The court awarded damages of $67,922.85 plus interest, and this appeal followed.
II.
A.
We start with the proposition that the right of employees to engage in sympathy strikes is protected under the National Labor Relations Act. Yet this right can be waived in a collective bargaining agreement. See NLRB v. Rockaway News Supply Co., 345 U.S. 71, 73 S.Ct. 519, 97 L.Ed. 832 (1953). In addition, the Union here has not challenged the district court’s finding that the Union authorized the sympathy strike. Cf. Carbon Fuel Co. v. UMW, 444 U.S. 212, 100 S.Ct. 410, 62 L.Ed.2d 394 (1979) (union not liable for wildcat strike). Thus the question presented is whether by virtue of the terms of the 1976 contract the production and maintenance employees waived their right to refuse to cross the drivers’ picket line.
The extent of the waiver in a collective bargaining agreement of the right to strike “ ‘turns upon the proper interpretation of the particular contract . . . [which] must be read as a whole and in light of the law relating to it when made.’ ” Food Fair Stores, Inc. v. NLRB, 491 F.2d 388, 395 (3d Cir. 1974), quoting Mastro Plastics Corp. v. NLRB, 350 U.S. 270, 279, 76 S.Ct. 349, 356, 100 L.Ed. 309 (1956). Moreover, we have held “that a waiver of a statutory right must be clearly and unmistakably established, and that express language will not be read expansively.” United Steelworkers v. NLRB, 536 F.2d 550, 555 (3d Cir. 1976) (waiver of certain grievance procedures). Accord, e. g., Gary Hobart Water Co. v. NLRB, 511 F.2d 284, 287 (7th Cir.) (sympathy strike), cert. denied, 423 U.S. 925, 96 S.Ct. 269, 46 L.Ed.2d 252 (1975).
[1185]*1185These waiver principles are complicated in the context of a sympathy strike because the union’s no-strike obligation may be created in one of two ways: by implication from the arbitration clause or by an express clause in the contract. See Gateway Coal Co. v. UMW, 414 U.S. 368, 94 S.Ct. 629, 38 L.Ed.2d 583 (1974). In United States Steel Corp. v. UMW (U.S. Steel II), 548 F.2d 67 (3d Cir. 1976), cert. denied, 431 U.S. 968, 97 S.Ct. 2926, 53 L.Ed.2d 1063 (1977), U.S. Steel’s employees refused to cross a picket line at another employer’s plant. We held that the sympathy strike did not violate the implied no-strike obligation arising out of the arbitration clause in the collective bargaining agreement.
In U.S. Steel II we reserved the question of whether an express no-strike clause like we have here would waive the right to engage in a sympathy strike. Given that waiver turns on the facts of each case, implied and express no-strike obligations present different factual and analytical problems. Where the no-strike obligation is express in the contract, there are a number of facts relevant to whether the union intended to waive the right to engage in a sympathy strike that simply are not present in cases involving an implied no-strike obligation. For example, with an express clause, the court can determine its meaning by looking to the language of the clause, the structure of the contract, the bargaining history, and any other relevant conduct of the parties that shows their understanding of the contract. While we do not mean to suggest that this is an exclusive list, we feel that the factual nature of the waiver inquiry requires an examination of those factors in any case involving an express no-strike clause where there is no explicit reference in the contract to sympathy strikes.
B.
Initially, we must consider whether the language of the no-strike clause itself waives the right to sympathy strike. The contract here contains a broad, general no-strike clause. As the district court correctly noted, there is no picket line clause,1 nor does the contract expressly refer to sympathy strikes. Although the language is broad in the sense that it refers to “any strike,” as in so many areas of labor law, seemingly express language may not be read out of the context of other legal principles. Several courts have concluded that a broad, general no-strike clause in and of itself is not a clear and unmistakable waiver of the right to sympathy strike. E. g., NLRB v. C. K. Smith & Co., 569 F.2d 162 (1st Cir. 1977), cert. denied, 436 U.S. 957, 98 S.Ct. 3070, 57 L.Ed.2d 1122 (1978). We agree with that result for two reasons.
First, the rationale underlying U.S. Steel II, supra, leads us to the conclusion that general language, by itself, is not explicit enough to waive the right to sympathy strike. In that case, we relied on the notion of coterminous interpretation, an idea that grew up largely in the area of implied no-strike obligations. Coterminous interpretation means that if the subject matter of the strike is arbitrable, then the strike violates the no-strike clause. The theory underlying [1186]*1186this is that the no-strike clause is a quid pro quo for the arbitration clause. See generally Gateway Coal Co., supra. In short, the obligation to not strike is read to be an obligation to not strike over arbitrable issues.
Applying these principles to the sympathy strike and the implied no-strike obligation in U.S. Steel II, we noted that with a sympathy strike, the subject matter of the strike is a dispute between the primary strikers and their employer and thus is not subject to arbitration between the sympathy strikers and their employer. In short, the strike is not “over any dispute” between the employer and the sympathy strikers. See U.S. Steel II, 548 F.2d at 73. Accordingly, we concluded in that case that because the subject matter of the strike was not arbitrable between the employer and the sympathy strikers, the sympathy strike did not violate the implied no-strike obligation.
We find this reasoning applicable where there is an express no-strike clause in the contract. The quid pro quo rationale underlying coterminous interpretation also applies where the union actually gives up its right to strike instead of having it implied from the arbitration clause. When faced with an express no-strike clause, the Supreme Court has applied the principles already discussed. For example, in Buffalo Forge Co. v. United Steelworkers, 428 U.S. 397, 96 S.Ct. 3141, 49 L.Ed.2d 1022 (1976), the Court was confronted with the question of whether a sympathy strike may be enjoined pending arbitration of the question of whether the strike violated the express no-strike clause in the contract. The Court first held that the applicability of the no-strike clause to the sympathy strike was arbitrable.2
Turning to the availability of injunctive relief, the Court carefully distinguished the arbitrability of the subject matter of the strike from the arbitrability of the applicability of the no-strike clause to the sympathy strike:
The District Court found, and it is not now disputed, that the strike was not over any dispute between the Union and the employer that was even remotely subject to the arbitration provisions of the contract. The strike at issue was a sympathy strike in support of sister unions negotiating with the employer; neither its causes nor the issue underlying it was subject to the settlement procedures provided by the contracts. .
Id. at 407-08, 96 S.Ct. at 3147-3148. Furthermore, the Court expressly relied on the quid pro quo theory to support its analysis. See id. at 407, 96 S.Ct. at 3147. The Court concluded that because the subject matter of the strike was not arbitrable between the sympathy strikers and their employer, the strike could not be enjoined pending arbitration of the scope of the express no-strike clause.
The relevance of Buffalo Forge is the recognition that, absent some evidence to the contrary, the quid pro quo theory underlying coterminous interpretation applies where there is an express no-strike clause in the contract. Normally, the employer will not agree to arbitration unless he gets an agreement from the union that it will not strike over those arbitrable issues. In addition, in the normal case the union will not agree to a no-strike clause that extends beyond the arbitration clause.
Moreover, the contract here supports coterminous interpretation. The arbitration clause is expressly tied to disputes between the production and maintenance employees and the Employer. As noted previously, the contract defines arbitrable grievances as disputes between the parties “arising under or out of” the contract. Nowhere does the contract mention the rights of the drivers or any other employees but the production and maintenance employees. See note 5 infra and accompany[1187]*1187ing text. Thus the definition of arbitrable grievances means that the production and maintenance employees could not have invoked arbitration over the dispute between the drivers and the Employer.
Although we realize that coterminous interpretation must be applied to the facts in each case, see Gateway Coal Co., supra, 414 U.S. at 382, 94 S.Ct. at 639, we believe that the reasoning behind it leads to the conclusion that a no-strike clause, without more, does not waive the right to sympathy strike. Coterminous interpretation rests on a perception of labor relations that has equal force where there is an express no-strike clause. Without evidence to the contrary, it is proper to presume that the no-strike clause is not broader than the arbitration clause. Thus we feel that where the sympathy strikers and their employer cannot arbitrate the subject matter of the primary dispute, a generally worded no-strike clause does not bar the sympathy strike.
A second source of support for the conclusion that broad, general language will not waive the right to sympathy strike is Mas-tro Plastics Corp. v. NLRB, 350 U.S. 270, 76 S.Ct. 349, 100 L.Ed. 309 (1956). There, the Supreme Court held that a broad, general no-strike clause did not waive the right to engage in unfair labor practice strikes. The Court noted that broad phrases like “any strike” should be read in light of the rest of the contract. The Court then noted that the contract, taken as a whole, dealt with the economic relations between the unfair labor practice strikers and their employer, such as wages, hours, and so forth. In effect, the no-strike clause was a promise by the union not to strike over matters covered by the contract. See id. at 281-83, 76 S.Ct. at 357-358.3
Mastro Plastics is a helpful analogy. Here, as there, the dispute between the production and maintenance employees and the Employer is not over anything covered by the 1976 contract. As already noted, the contract, taken as a whole, does not cover the drivers and their relation with the Employer. See generally note 5 infra and accompanying text. As in Mastro Plastics, it is proper to read the no-strike clause as limited to strikes over matters covered by the contract. Thus under Mastro Plastics the no-strike clause does not waive the right to sympathy strike because the dispute is not over the economic relations between the sympathy strikers and their employer as they are explicated in the 1976 contract. See generally NLRB v. C. K. Smith & Co., 569 F.2d 162, 167 (1st Cir. 1977), cert. denied, 436 U.S. 957, 98 S.Ct. 3070, 57 L.Ed.2d 1122 (1978). See also Suburban Transit Corp. v. NLRB, 536 F.2d 1018, 1021-22 (3d Cir. 1976) (strike violated no-strike clause because even though the strike was over a dispute with the union, it also involved a dispute with the employer).
Accordingly, we hold that a broad no-strike clause that is generally worded does not constitute a clear and unmistakable waiver of the right to sympathy strike. Absent some contrary evidence, the notion that the no-strike clause is the quid pro quo for the arbitration clause applies with equal force where there is an express no-strike clause. Relevant Supreme Court precedent, as shown by both Buffalo Forge and Mastro Plastics, supports the conclusion that a broadly worded no-strike clause does not waive the right to strike over nonarbitrable matters that are not covered by the strikers’ contract. Moreover, this accords with the general rule that waiver must be clear [1188]*1188and unmistakable and that explicit language will not be read expansively.
C.
If we were writing on a clean slate, we might opt for a rule that would end the inquiry by asking whether the language of the contract explicitly deals with the right of employees to sympathy strike. Such an approach would have the benefit of reducing the litigation engendered by uncertainty over whether any of the wide variety of factors usually considered will constitute waiver.
However, we do not feel free to adopt such an approach and therefore now turn to the factors examined by the district court to determine whether they constitute sufficient evidence of waiver. Initially, we note that because the parties offered no evidence as to the negotiation of the 1976 contract, we need not decide whether evidence of bargaining history could overcome the result here. See NLRB v. Rockaway News Supply Co., 345 U.S. 71, 73 S.Ct. 519, 97 L.Ed. 832 (1953) (evidence that employer rejected a clause offered by union to effect that employees could refuse to cross picket line).
The first factor relied on by the district court to find waiver was a finding that the arbitration and no-strike clauses here were “functionally independent.” Its reasoning essentially was that where the no-strike clause and the arbitration clause are related, then the no-strike clause only covers arbitrable issues, but where they are independent, the no-strike clause is broader.
The district court never explained the precise meaning of the phrase “functionally independent.” It did refer to “a no-strike clause which was included in the grievance procedures of a contract or which was directly tied to arbitrable matters.” If by this the court meant that the language or structure of the contract somehow had to tie the no-strike clause and the arbitration clause together,4 our previous discussion disposes of that. Because the no-strike clause normally is the quid pro quo for the arbitration clause, the normal assumption is that they are functionally related, even if the contract does not explicitly condition one on the other. Physical separation or lack of cross-reference in the contract cannot constitute clear waiver of the right to sympathy strike.
On the other hand, the district court might have been referring to Section 3 of Article 16, which states that the “provisions of [the no-strike clause] . . . shall not be subject to grievance or arbitration, for the purpose of assessing damage or securing specific performance, or any other matter.” This language would seem to mean only that the question of whether a particular strike violated the no-strike clause is not arbitrable. See note 2 supra. As already noted in our discussion of Buffalo Forge, that is analytically distinct from whether the subject matter of the strike is arbitra-ble. Because our decision rests on the latter question, Section 3 has no impact on our reasoning.
Next, the district court relied on the law existing at the time the contract was made to infer waiver of the right to sympathy strike. It noted that in 1976, several courts had held that where the no-strike clause and the arbitration clause were tied together, the no-strike clause did not waive the right to sympathy strike. See note 4 supra. From these cases, the court reasoned that “at the time the contract was executed there was an established distinction in the case law between broad, independent no-[1189]*1189strike clauses and more limited, dependent no-strike clauses.” The court concluded that because here the no-strike clause was independent, the parties intended the no-strike clause to be broader than the arbitration clause.
Even assuming that the cases cited by the district court rested on the fact that the no-strike clause and the arbitration clause were “functionally tied together,” it does not follow that there was a distinction between independent and dependent clauses. The mere fact that dependent clauses preclude waiver does not necessarily mean that independent clauses will result in waiver. Indeed, the quid pro quo theory, which was established at the time the present contract was signed, militates against such a distinction. Moreover, the district court cited no case, and research reveals none, where a court had held that independent clauses would lead to waiver of the right to sympathy strike. Because we can find no clear distinction in the 1976 case law between independent and dependent clauses, the law at the time of the signing of the contract is not clear and unmistakable evidence that the union intended to waive the right to sympathy strike.
The district court also relied on the conduct of the parties prior to and during the strike here to determine their understanding of the contract as it related to whether the sympathy strike was prohibited. We of course recognize the danger inherent in utilizing such evidence because it may not reflect the parties’ intention of the time of the execution of the contract. Nevertheless, the district court considered such evidence in reaching its result, and we feel constrained to address it. The district court relied on the following events:
(1) The district court found that when Jones, the manager of the plant, told the president of the Union that a strike would violate the 1976 contract, the president replied “I don’t care.” In fact, Jones testified as follows:
Q: Will you relate to the Court what you told [the president] at that time?
A: Well, our determination was that after we had cancelled Countrywide Personnel’s agreement with us, that the drivers would fall back into the plant contract, the production and maintenance workers’ contract, and the union’s position was that there should be two different contracts. And because we were not able to reach a decision that day, [the president] stated that they were going on strike. And I stated during the meeting that if they did, they would be in violation of the production and maintenance workers’ contract.
Q: What was his reply to that?
A: [He] said it didn’t matter. The time to strike the Coca-Cola plant was in the summertime, and he wasn’t going to wait until the issue was resolved.
This testimony is not clear and unmistakable evidence that the president believed the contract waived the right of the production and maintenance employees to strike. Initially, when the president said “they were going on strike,” it is unclear whether he meant the drivers, the production and maintenance employees, or both. Thus the entire exchange is ambiguous because we cannot tell what kind of strike Jones and the president were talking about.
Moreover, given that Jones had just said that the drivers were covered by the 1976 contract, then Jones’s reply to the threatened strike — that “it” would violate the contract — could mean that he was saying that the drivers’ strike would violate the 1976 contract. Thus the president’s remark is ambiguous because by saying “it didn’t matter,” the president could have meant that Jones’s comment about the strike violating the 1976 contract was irrelevant because the president believed the drivers’ strike would not violate any contract.
(2) During the strike, the Eastern Conference of Teamsters sent a telegram to the local stating that the sympathy strike violated the 1976 contract. We find this to fall short of the standard of proof. The [1190]*1190Eastern Conference was not involved in negotiating the 1976 contract, making its views less than persuasive on the intent of the Union to waive the right to sympathy strike. Moreover, when the production and maintenance employees sympathy struck in March 1976, the Conference remained silent.
(3) The district court found that the union shop steward told the employees that a sympathy strike would violate the 1976 contract. The record is at variance with this finding. The testimony reads:
A: I went and I told the production personnel that there was liable to be a strike in the morning, but I also told them that under Article 16 in the contract, that if they — and that each man was to use his own judgment about going to work.
A statement that each employee should use his own judgment is not evidence that the steward thought a sympathy strike would violate Article 16.
(4) Some of the members of the Employer’s management told the Union that a sympathy strike would violate Article 16. We decline to hold that an employer’s statements, without more, are evidence of the union’s intent to waive the right to sympathy strike.
In short, none of this evidence, singly or collectively, supports an inference that the Union believed a sympathy strike by the production and maintenance employees would violate the 1976 contract.
Finally, it does not matter that all employees were represented by the same local or that only one employer was involved. In United States Steel Corp. v. UMW (U.S. Steel III), 593 F.2d 201 (3d Cir. 1979), one local of the UMW struck U.S. Steel, and other UMW locals representing U.S. Steel employees went out on sympathy strikes. We held that, unlike in U.S. Steel II, the implied no-strike obligation barred the sympathy strike in question. U.S. Steel III employed a two-prong test to reach this result, and neither of the two prongs is satisfied here.
The first prong of the U.S. Steel III test was that the dispute between the primary employees and their employer must be subject to arbitration. 593 F.2d at 208. Here, the drivers never signed a contract with the Employer. The district court found that negotiations with the drivers continued after the contract with the production and maintenance employees was signed right up until the drivers became employees of Countrywide. Indeed, Article 1 of the 1976 contract is a recognition clause, and it is limited to the production and maintenance employees.5 Nowhere does it mention that the drivers are covered. Thus because the drivers were not parties to the 1976 contract, their dispute with the Employer was not arbitrable.
The second prong of the U.S. Steel III test dealt with the fact that although “technically” the sympathy striker’s local could not arbitrate the dispute between the employer and the primary strikers, the dispute essentially was between the UMW and U.S. Steel. We noted that both the primary strikers and the sympathy strikers were subject to the same collective bargaining agreement that had been negotiated by their international, not the locals. See id. at 208-09. Here, by contrast, the drivers and the production and maintenance employees were not subject to the same contract. Indeed, the drivers seem to have had no contract at all.
To summarize, we hold that a broad, general no-strike clause does not constitute evidence of clear and unmistakable waiver of the right to sympathy strike. Absent evidence to the contrary, where the subject matter of the strike is not arbitrable between the sympathy strikers and their employer and where the contract read as a [1191]*1191whole indicates that the no-strike clause is limited to issues covered by the contract, such general language will not be read to cover sympathy strikes. Here, none of the evidence satisfies the quantum of proof necessary to overcome this result. The parties presented no evidence of bargaining history, and neither the law at the time of the signing of the contract nor the parties’ conduct during the events here supply evidence from which an inference was warranted that the Union intended to waive the right to sympathy strike.
III.
The judgment of the district court will be reversed.