MESKILL, Circuit Judge:
Maria Vasquez appeals from a judgment entered in the United States District Court for the Eastern District of New York, Thomas C. Platt, Judge, convicting her, after a plea of guilty, of one count of knowingly and intentionally using a communication facility in connection with the commission of a narcotics-related felony, in violation of 21 U.S.C. § 843(b).1 Appellant’s guilty plea was entered pursuant to a court-approved agreement preserving her right to appeal the court’s denial of her motion to suppress certain evidence.2
The evidence that Vasquez seeks to have suppressed was seized in the course of a [1340]*1340warrantless search conducted by agents of the Drug Enforcement Administration shortly after Vasquez and Luis Flores, another passenger apparently travelling with her, arrived at La Guardia Airport on a flight from Chicago. Vasquez contends that the evidence was obtained as the result of an unconstitutional stop in the course of which the agents made an unconstitutional search. Specifically, she argues (1) that the agents lacked reasonable cause to stop and question her, and thus the evidence seized in the course of the stop must be excluded as the fruit of an unconstitutional seizure, and (2) that Flores’ purported consent to the warrantless search of the luggage in his possession was not freely and voluntarily given, and thus the evidence found pursuant to that invalid consent must be excluded as the fruit of an unconstitutional search. Our review of the record compels us to reject both contentions and we therefore affirm.
I. Background
After a two-day suppression hearing, at which the three arresting agents and an airport skycap testified, Judge Platt found the relevant facts as follows.3 On April 4, 1978, a team of DEA Special Agents assigned to La Guardia Airport was observing passengers arriving on an afternoon flight from Chicago, which has been identified by the DEA as a “source” city from which couriers frequently transport illicit drugs to New York via regularly-scheduled commercial flights. Vasquez and Flores were the last passengers to disembark. Although they were conversing as they walked down the first ramp, they separated when they reached the corridor leading to the waiting room. As Flores proceeded to the baggage area, Vasquez trailed behind him, glancing frequently over her shoulder as she walked and, on at least two occasions, stopping to make a complete turn while surveying the other people in the terminal. During a five minute wait in the baggage claim area, Vasquez and Flores stood several yards apart, occasionally making eye contact but, according to the agents’ testimony, giving no signs of recognition. When the luggage was placed on the carousel, Flores removed two bags, neither of which bore any identification. One of the bags was secured with a small metal padlock.
After retrieving the luggage, Flores summoned a skycap. One of the DEA agents, Gerard Whitmore, then saw Flores tear two baggage claim checks off his boarding pass, giving the claim checks to the skycap and returning the boarding pass to his pocket. When the skycap inquired as to Flores’ destination, Flores initially responded “Brooklyn,” but after being corrected by Vasquez, Flores again addressed the skycap and said “the Bronx.” After this exchange, Vasquez again moved away from Flores. As the skycap led the way to the taxi-stand, Flores followed him closely while Vasquez followed Flores at some distance.
When the skycap began to load the luggage into a taxi, Agent Whitmore identified himself as a federal narcotics agent and asked the skycap to hold up for a moment. According to the skycap’s testimony, this request was made in a quiet and polite manner. Agent Whitmore then addressed Flores, asking whether he spoke English. Flores responded in the affirmative. Agent Whitmore then asked if he could see Flores’ airline ticket and some identification. In response, Flores produced a driver’s license but said that he did not have an airline ticket. Agent Whitmore then asked Flores whether the two bags were his. Flores did not reply but the skycap handed the two claim checks to Agent Whitmore. At this point Agent Sears, who along with Agent Trustey had been questioning Vasquez while Whitmore spoke to Flores, informed Agent Whitmore that Vasquez had produced no identification but had stated that her name was Maria Vasquez, that the luggage was not hers, and that Mr. Flores had her airplane ticket. Agent Whitmore again asked Flores for the tickets and in response Flores showed him two consecutively numbered tickets made out to “Mr. and Mrs. Alcaide.” The tickets, purchased for cash [1341]*1341on that very day, were both one-way from Chicago to New York.
Agent Whitmore again asked Flores whether the luggage was his. Flores, now exhibiting signs of nervousness such as shaking hands and choppy speech, replied that the bags were his but that he did not know what was in them because they had been packed by someone else. Upon receiving this response, Whitmore informed Flores that he had reason to believe that the luggage contained narcotics. Whitmore also told Flores that unless Flores gave his permission Whitmore would have to seek a warrant in federal court before opening the luggage. Flores replied that Whitmore should “check out” the luggage because that was his job. Agent Whitmore asked Flores and Vasquez whether they would mind stepping inside, and the two suspects and the three agents returned to the terminal building. Flores and Vasquez were again advised by Agent Whitmore that he had no authority to open the bags unless they consented and that without their consent he would have to seek a search warrant in court. Flores again told Whitmore to open the bags, while Vasquez continued to indicate that the bags were not hers. When the bags were opened the agents found several packages of heroin. Flores and Vasquez were arrested, given the appropriate warnings, Miranda v. Arizona, 384 U.S. 436, 86 S.Ct. 1602, 16 L.Ed.2d 694 (1966), and driven to the DEA office at Kennedy Airport for processing.
The uncontradicted testimony of the agents and the skycap was to the effect that the agents were not in uniform, that all questioning was carried on in a conversational tone of voice, that no weapons were displayed, and that neither Vasquez nor Flores was touched by any of the agents prior to the formal arrests.
II. The Stop
During the current term this Court has heard a number of appeals challenging the admissibility of evidence seized by DEA agents who have stopped suspected narcotics couriers arriving at La Guardia and obtained their consent to conduct a search.4 The legal standards against which we must assess these stops are therefore familiar, as is the scenario which typically leads up to these encounters.
As the Supreme Court has recently reaffirmed, the essential purpose of the Fourth Amendment is to impose a standard of reasonableness on government officials in order to safeguard the privacy and security of individuals against arbitrary invasion. Delaware v. Prouse, 440 U.S. 648, 654, 99 S.Ct. 1391, 1396, 59 L.Ed.2d 660 (1979). Therefore, the Prouse Court explained,
the permissibility of a particular law-enforcement practice is judged by balancing its intrusion on the individual’s Fourth Amendment interests against its promotion of legitimate governmental interests. Implemented in this manner, the reasonableness standard usually • requires, at a minimum, that the facts upon which an intrusion is based be capable of measurement against “an objective standard,” whether this be probable cause or a less stringent test.
Id. (footnotes omitted). When a seizure entails “the kind of intrusion involved in an arrest,” the reasonableness standard of the Fourth Amendment generally requires that the officers act on no less than probable cause. Dunaway v. New York, 442 U.S. 200, 208, 99 S.Ct. 2248, 2254, 60 L.Ed.2d [1342]*1342824 (1979).5 However, it has long been the law that a less intrusive stop may be reasonable under the Fourth Amendment if the facts upon which the intrusion is based meet the “less stringent” although still “objective” standard of “reasonable suspicion.” Terry v. Ohio, 392 U.S. 1, 88 S.Ct. 1868, 20 L.Ed.2d 889 (1968). See also Adams v. Williams, 407 U.S. 143, 145-46, 92 S.Ct. 1921, 32 L.Ed.2d 612 (1972). It is clear that the investigative stop at issue in this case does not “fit comfortably within the traditional concept of an ‘arrest’ ” because the intrusion involved is “so much less severe.” Dunaway v. New York, supra, 442 U.S. at 209, 99 S.Ct. at 2254; United States v. Vasquez-Santiago, 602 F.2d 1069, 1071 (2d Cir. 1979). Rather, the stop fits within the narrow and circumscribed category of minimally' intrusive seizures first recognized in Terry v. Ohio, supra, and therefore may be deemed justified under the Fourth Amendment if it can be demonstrated, solely on the basis of specific and articulable facts and the rational inferences to be drawn therefrom, that the intrusion was based on reasonable suspicion. United States v. Price, 599 F.2d 494, 499 (2d Cir. 1979). See also Brown v. Texas, - U.S. -, 99 S.Ct. 2637, 61 L.Ed.2d 357 (1979); United States v. Brignoni-Ponce, 422 U.S. 873, 95 S.Ct. 2574, 45 L.Ed.2d 607 (1975).
The constitutional standard of “reasonableness” takes into account both governmental and private interests. The public interest is measured by examining the need for the stop, and the individual’s interest is calculated by assessing the gravity of the intrusion suffered. United States v. Price, supra, 599 F.2d at 499; United States v. Magda, 547 F.2d 756, 758 (2d Cir. 1976), cert. denied, 434 U.S. 878, 98 S.Ct. 230, 54 L.Ed.2d 157 (1977), citing Terry v. Ohio, supra, 392 U.S. at 21, 88 S.Ct. 1868. “The need for a stop depends on factors such as the seriousness of the offense suspected, the consequences of delay on the part of the officers, and the likelihood of the detainee’s involvement in the offense suspected.” United States v. Price, supra, 599 F.2d at 500. That the offense suspected is heroin trafficking and that the departure of the suspect appears imminent are both factors increasing the need for a stop. Id.; United States v. Oates, 560 F.2d 45, 59 (2d Cir. 1977); United States v. Magda, supra, 547 F.2d at 759; United States v. Santana, 485 F.2d 365, 368 (2d Cir. 1973), cert. denied, 415 U.S. 931, 94 S.Ct. 1444, 39 L.Ed.2d 490 (1974).
As to the likelihood of the appellant’s involvement in the suspected crime, according to testimony credited by Judge Platt, the agents’ stop of Vasquez and Flores was based on the following observations:
1. Vasquez and Flores arrived on a flight from Chicago, a known “source” city. See United States v. Vasquez-Santiago, supra, 602 F.2d. at 1072; United States v. Price, supra, 599 F.2d at 500.
2. Vasquez and Flores were the last passengers to disembark.
3. Although Vasquez and Flores were engaged in conversation as they disembarked, when they reached the corridor they stopped and separated. Cf. United States v. Vasquez-Santiago, supra, 602 F.2d. at 1072.
4. Vasquez followed Flores at a distance of about 10 yards, keeping Flores in view and frequently glancing behind her (“to see if she was being followed” in Judge Platt’s assessment). On two occasions she stopped and made a full turn in order to survey [1343]*1343the area. Cf. United States v. Vasquez-Santiago, supra, 602 F.2d. at 1071; United States v. Price, supra, 599 F.2d at 496.
5. In the baggage claim area, Vasquez remained about ten yards away from Flores. Although the two made frequent eye contact, according to the agents’ testimony no signs of recognition were exchanged.
6. Although she waited for the baggage to arrive, Vasquez claimed nothing.
7. When Flores gave his destination to the skycap, Vasquez corrected him, again moved away from Flores, and then proceeded to follow Flores and the skycap at a distance of ten to fifteen feet.
8. The two bags claimed by Flores bore no identification. See United States v. Price, supra, 599 F.2d at 496; United States v. Rico, 594 F.2d 320, 322 (2d Cir. 1979). One of them was secured with a small padlock identical to those the agents had observed, on two occasions during the preceding year, attached to luggage which had arrived from Chicago and which was found to contain heroin.
We agree with Judge Platt’s conclusion that these observations and the rational inferences to be drawn therefrom rendered reasonable the minimally intrusive stop under consideration.
In reaching this determination we keep in mind two principles:
The circumstances surrounding a stop “are not to be dissected and viewed singly; rather they must be considered as a whole.” ... In addition, these circumstances “are to be viewed through the eyes of a reasonable and cautious police officer on the scene, guided by his experience and training.”
United States v. Price, supra, 599 F.2d at 501, quoting, inter alia, United States v. Oates, supra, 560 F.2d at 61; United States v. Magda, supra, 547 F.2d at 758. Thus while any one of the specific factors noted by the DEA agents might appear unexceptional if viewed in isolation, in our view the composite picture would appear sufficiently suspicious, at least to the trained eye,6 to warrant a minimally intrusive stop for purposes of further investigation. “[S]ome patterns of behavior which may seem innocuous enough to the untrained eye may not appear so innocent to the trained police officer who has witnessed similar scenarios numerous times before.” United States v. Oates, supra, 560 F.2d at 61. Even the fact that the conduct of Vasquez and Flores might possibly have been consistent with innocence does not invalidate the stop. As we have noted before, “reasonable” cause for suspicion of narcotics trafficking may suffice to justify a minimally intrusive stop. “Certainty is not a constitutional prerequisite . . . .” United States v. Price, supra, 599 F.2d at 502.
Thus the initiation of the stop was not unreasonable in this case. Nor did the scope of the intrusion exceed what was warranted under the circumstances. There was no evidence of harassment, intimidation, physical restraint, humiliation or prolonged questioning. See United States v. Price, supra, 599 F.2d at 500; United States v. Magda, supra, 547 F.2d at 759. After Agent Whitmore identified himself and determined that Flores spoke English, the agent’s first request was to see some identification as well as Flores’ airplane ticket. In view of the conduct observed by Agent Whitmore, this initial stop for the purpose [1344]*1344of limited questioning falls within the “sui generis” category of “narrowly defined less intrusive seizure[s]” that satisfy the Fourth Amendment “on grounds less rigorous than probable cause.” Dunaway v. New York, supra, 442 U.S. at 210, 99 S.Ct. at 2255; see United States v. Brignoni-Ponce, supra, 422 U.S. at 880, 95 S.Ct. 2574.
Flores’ assertion that he had no ticket could serve only to heighten the suspicion of a reasonable observer who, like Whitmore, had just seen Flores put his ticket in his pocket. Cf. United States v. Rico, supra, 594 F.2d at 323. Since Vasquez had simultaneously told the agents that Flores was holding her ticket, Whitmore also cannot be said to have acted unreasonably in repeating his request for the tickets. When, in response, Flores produced tickets bearing a name matching neither the name given by Flores nor that given by Vasquez, yet another objectively suspicious factor was added to the earlier observations of the agents. When, after one more question from Agent Whitmore, Flores volunteered that although the bags were his he did not know what was in them, the compelling need for further questioning of both suspects was manifest. Since Vasquez and Flores were apparently acting in concert while trying to appear not to be doing so, it was not unreasonable in this case for the agents to consider the answers and responses of both in determining the propriety of continuing the questioning of each.
Although we share Judge Oakes’ view that the courts should not countenance the chipping away, by over-zealous law enforcement officers, of the protections of the Fourth Amendment, we do not share his belief that today’s decision and the precedents on which it is grounded have, in effect, carved out a new exception to the law governing searches and seizures, narrowed the scope of the Fourth Amendment, or broadened the scope of Terry v. Ohio, supra.
Like Judge Oakes we reject any suggestion that, in the absence of border search or special safety justifications, a stop made at an airport may be judged by criteria different from those governing stops made anywhere else in this country. There is no separate body of Fourth Amendment law applicable to domestic airport stops by the DEA. Where Vasquez was stopped is a factor to be considered in determining whether the stop was reasonable, but it is not a factor to be considered in determining the standard against which the stop must be judged. That standard is, of course, dictated by the Fourth Amendment.
Clearly then, we must reject the suggestion in the dissent that our Court has narrowed the scope of Fourth Amendment protection in the recent series of “DEA-airport” stop cases. The precise purpose of both the suppression hearing below and of our review has been to subject the actions of Agent Whitmore, the law enforcement officer in the field, to examination by neutral and detached judicial officers whose duty is to determine the constitutionality of his conduct by the application of objective standards which give weight only to specific and articulable factors justifying that conduct.
We cannot agree with the characterization of this case and its predecessors as “expansions” of Terry v. Ohio, supra. The facts of Terry are uncomplicated and worth recalling. One afternoon, while patrolling the downtown area of Cleveland, Ohio, one Officer McFadden observed that two men whom he had never seen before were standing on a corner. Officer McFadden was “unable to say precisely what first drew his eye to them” except for the feeling that they “didn’t look right,” 392 U.S. at 5, 88 S.Ct. at 1871. Officer McFadden continued to watch the two men as they walked repeatedly past a particular store window, one at a time, paused to look inside, and returned to the corner to confer. After many repetitions, the two men walked off, following the path taken by a third man who had spoken with them briefly a few minutes earlier.
Believing on the basis of these observations that the men were “casing a job,” id. at 6, 88 S.Ct. 1868, Officer McFadden approached the three men, identified himself as a police officer and asked for their [1345]*1345names.7 “When the men ‘mumbled something’ in response to his inquiries, Officer McFadden grabbed petitioner Terry, spun him around . . . and patted down the outside of his clothing.” Id. at 7, 88 S.Ct. at 1872. Feeling a pistol in Terry’s pocket, McFadden seized it. Terry was subsequently convicted of carrying a concealed weapon, and the Supreme Court, for the first time, passed upon the constitutionality of the “stop and frisk.”
Understandably the Court focused primarily on the “frisk” aspect of this interaction, for it was the frisk that had yielded the pistol that Terry sought to have suppressed. The Court emphasized that the crux of the case was “not the propriety of Officer McFadden’s taking steps to investigate petitioner’s suspicious behavior, but rather, whether there was justification for McFadden’s invasion of Terry’s personal security by searching him for weapons in the course of that investigation.” Id. at 23, 88 S.Ct. at 1881. In fact, the Court “assume[d]” that up to the initiation of physical contact “no intrusion upon constitutionally protected rights had occurred,” and declined to decide anything concerning the “constitutional propriety of an investigative ‘seizure’ upon less than probable cause for purposes of ‘detention’ and/or interrogation.” Id. at 19 n.16, 88 S.Ct. at 1879.
We can find nothing in Terry or its progeny to support the view, implicit in Judge Oakes’ dissent today, that the right of a police officer to stop a person reasonably suspected of engaging in criminal activity, for the purpose of asking a few questions, hinges on the reasonable suspicion that the suspect is armed and dangerous. The cases suggest otherwise. Chief Justice Warren, speaking for the Court in Terry, recognized “that a police officer may in appropriate circumstances and in an appropriate manner approach a person for purposes of investigating possibly criminal behavior even though there is no probable cause to make an arrest,” and noted that “[i]t was this legitimate investigative function Officer McFadden was discharging when he decided to approach [the suspects].” Id. at 22, 88 S.Ct. at 1880 (emphasis added). Justice Harlan, in concurrence, grappled more directly with the pre-frisk aspect of the stop. “[I]f the frisk is justified in order to protect the officer during an encounter with a citizen, the officer must first have constitutional grounds to insist on an encounter, to make a forcible stop.” Id. at 32, 88 S.Ct. at 1885 (emphasis in original).
The facts of this case are illustrative of a proper stop and an incident frisk. Officer McFadden . . . had observed' circumstances that would reasonably lead an experienced, prudent policeman to suspect that Terry was about to engage. in burglary or robbery. His justifiable suspicion afforded a proper constitutional basis for accosting Terry, restraining his liberty of movement briefly, and addressing questions to him .
Id. at 33, 88 S.Ct. at 1886 (emphasis added).
Four years later, in Adams v. Williams, supra, 407 U.S. at 146, 92 S.Ct. at 1923, the Court wrote: “So long as the officer is entitled to make a forcible stop, and has reason to believe that the suspect is armed and dangerous, he may conduct a weapons search limited in scope to [a] protective purpose.” (emphasis added, footnote omitted). Again, the implication is strong that entitlement to make the stop depends on a reasonable belief that the suspect is engaging in criminal activity, regardless of whether he is also armed and dangerous. See also United States v. Nieves, 609 F.2d 642 (2d Cir. 1979), and cases cited therein.
Nor, in our view, does Dunaway v. New York, supra, stand for the proposition that an officer may stop a suspect only in circumstances that would justify a frisk. Dunaway simply reaffirms the important principle that a maximal intrusion, even if technically short of arrest, must be based upon probable cause.
[1346]*1346Judge Oakes would delay judicial approval of what he terms a néw system of law enforcement until it can be demonstrated that the official conduct under challenge is the product of rulemaking and is not carried out in a discriminatory manner. As to the first suggestion, we note that it was the very different question of random stops, which are concededly based on neither the objective standard of probable cause nor the objective standard of reasonable suspicion, that concerned the Court in Delaware v. Prouse, supra, and prompted the observation that some objective standard or rule must guide the exercise of official discretion. Regarding Judge Oakes’ suggestion that Vasquez’s possibly Hispanic appearance played an impermissible role in the decision to stop her, we note that the evidence that would support such a claim is ambiguous at best. When improper police conduct is identified, it must and will be condemned by this Court. However, as the Supreme Court has recognized, evidence properly obtained in one case should not be excluded as a protest against the ever present possibility of abuse of evidence gathering techniques in another, hypothetical, case. Terry v. Ohio, supra, 392 U.S. at 14-15, 88 S.Ct. 1868.
Having determined that the stop of Vasquez did not violate her Fourth Amendment right to be free of unreasonable seizures, we need not consider whether the search of the luggage can logically be viewed as the “fruit” of that stop.
III. The Search
As noted above, Vasquez challenges not only the stop but the search that followed.8 However, we see no reason to [1347]*1347overturn the district court’s finding that Flores voluntarily consented to the search of the luggage.
First, the district court properly noted that when the government relies on consent in lieu of a warrant it bears the burden of proving that any purported consent was in fact voluntary rather than “the product of duress or coercion, express or implied,” Schneckloth v. Bustamonte, 412 U.S. 218, 227, 93 S.Ct. 2041, 2048, 36 L.Ed.2d 854 (1973); Bumper v. North Carolina, 391 U.S. 543, 88 S.Ct. 1788, 20 L.Ed.2d 797 (1968). Second, the district judge carefully considered the totality of all the circumstances in making his determination. Schneckloth v. Bustamonte, supra, 412 U.S. at 227, 93 S.Ct. 2041. The court found no overbearing conduct or threats of any kind on the part of the agents and credited the uncontradicted testimony that Flores had twice been advised of his right to refuse to consent — a factor weighing heavily in the determination of voluntariness. Id. Because it cannot be characterized as clearly erroneous, the district court’s finding of voluntariness must stand. United States v. Vasquez-Santiago, supra, 602 F.2d at 1073; United States v. Price, supra, 599 F.2d at 504.
As neither the stop nor the search violated appellant’s Fourth Amendment rights, the judgment of conviction is affirmed.