Was the monitoring by customs officials of a signal that disclosed the presence of an aircraft in public airspace an unconstitutional search or seizure under the Fourth Amendment because the terms of the warrant authorizing the signaling device required it to be removed before its signal was recorded? We hold it was not. The warrant violation did not change the detection of the defendant’s public activity into a Fourth Amendment violation. The evidence obtained by such monitoring should not have been suppressed.
I
On June 19, 1981, a United States Customs Agent filed an affidavit seeking court authorization to install an electronic tracking device, commonly called a beeper, inside a designated aircraft. In the affidavit, the agent alleged that probable cause existed to believe the aircraft would be used to import marijuana into the United States. Based on this affidavit, a United States Magistrate authorized the installation. The warrant required the beeper to be removed within thirty days after its installation. During the night of June 19, a customs agent installed the beeper in the interior of the aircraft, which was parked at a Seguin, Texas, airport.
On July 21, two days after expiration of the thirty-day time limit, a customs agent sought and was granted an extension of the original authorization. No further entry of the aircraft was made at that time. The extension order directed that the beeper be removed no later than August 19, which was thirty days from the date of the original expiration date. The installing agent was not on duty on August 19, and the beeper was not removed as the warrant required.
On August 22, customs officials began monitoring an aircraft emitting signals from a customs beeper. The target aircraft was periodically monitored by radar, sighted and followed by customs pilots, and intercepted when it landed. Customs officials then arrested Butts, the pilot of the target aircraft. Marijuana- and other evidence was found on the aircraft.
Butts was charged with importing marijuana into the United States, 21 U.S.C. §§ 960(a)(1), 952(a), with possession of marijuana with intent to distribute it, 21 U.S.C. § 841(a)(1), and with carrying a firearm during the commission of a felony, 18 U.S.C. § 924(c)(2). Before trial, Butts moved to suppress all evidence obtained by customs agents as a result of their monitoring of the beeper on August 22 and 23, the two days on which Butts was piloting the aircraft.1 The district court granted *1516Butts’s motion after conducting an evidentiary hearing. The government appealed the district court’s order pursuant to 18 U.S.C. § 3731.
A divided panel of this court affirmed the suppression order of the district court. United States v. Butts, 710 F.2d 1139 (5th Cir.1983). This holding was vacated by our action granting rehearing en banc. 5th Cir. Local R. 41.3.
II
In Katz v. United States, 389 U.S. 347, 88 S.Ct. 507, 19 L.Ed.2d 576 (1967), the Supreme Court developed the principles that currently control Fourth Amendment analysis:
[T]he Fourth Amendment protects people, not places. What a person knowingly exposes to the public, even in his own home or office, is not a subject of Fourth Amendment protection. [Citations omitted.] But what he seeks to preserve as private, even in an area accessible to the public, may be constitutionally protected.
Id. at 351, 88 S.Ct. at 511. The Court recently summarized these principles:
Consistently with Katz, this Court uniformly has held that the application of the Fourth Amendment depends on whether the person invoking its protection can claim a “justifiable,” a “reasonable,” or a “legitimate expectation of privacy” that has been invaded by government action. [Citations omitted.] This inquiry, as Mr. Justice Harlan aptly noted in his Katz concurrence, normally embraces two discrete questions. The first is whether the individual, by his conduct, has “exhibited an actual (subjective) expectation of privacy,” 389 U.S., at 361 [88 S.Ct. at 516], — whether, in the words of the Katz majority, the individual has shown that “he seeks to preserve [something] as private.” Id., at 351 [88 S.Ct. at 511]. The second question is whether the individual’s subjective expectation of privacy is “one that society is prepared to recognize as ‘reasonable,’ ” id., at 361 [88 S.Ct. at 516], — whether, in the words of the Katz majority, the individual’s expectation, viewed objectively, is “justifiable” under the circumstances. Id., at 353 [88 S.Ct. at 512]. [Citations omitted.]
Smith v. Maryland, 442 U.S. 735, 740-41, 99 S.Ct. 2577, 2580, 61 L.Ed.2d 220 (1979) (footnote omitted).
In United States v. Knotts, 460 U.S. 276, 103 S.Ct. 1081, 75 L.Ed.2d 55 (1983), the Supreme Court applied these principles to the use of a beeper as a law enforcement surveillance technique. In Knotts, officers acting without a warrant arranged with a chemical company to place a beeper inside a container of chloroform, which the company sold to a suspected illicit drug manufacturer. The officers then followed the vehicles in which the container was successively placed, maintaining contact both by visual surveillance and by monitoring the beeper. The officers lost the signal from the beeper for about an hour, but later relocated the signal, which was by then stationary at a site determined to be in or near Knotts’s cabin. The beeper was not used after officers determined that its signals indicated it had become stationary.
After watching for several days the cabin near which the beeper signals had come to rest, the officers used the tracking and beeper information to secure a search warrant for the cabin and found a drug factory. Id. at 1083-84. The district court denied Knotts’s motion to suppress the evidence based on the warrantless monitoring, and Knotts was convicted. On appeal, the Eighth Circuit reversed the conviction, concluding that the Fourth Amendment prohibited the warrantless monitoring. The Supreme Court reversed the Eighth Circuit.
The controlling significance of Knotts is that the Court’s analysis of Knotts’s Fourth Amendment rights separated its focus on the legality of the monitoring from *1517the legality of the warrantless installation. The Court noted that Knotts did not challenge the installation because he believed he lacked the standing necessary to make such a challenge. In passing, it observed that some circuits, including ours, had approved warrantless beeper installations. Then, without resolving whether the Knotts beeper was placed in the vehicle in an unconstitutional manner, the Court moved directly to the issue of monitoring. It concluded that because “[a] person travelling in an automobile on public thoroughfares has no reasonable expectation of privacy in bis movements from one place to another,” the use of a beeper to aid in monitoring or observing those movements was neither a search nor a seizure under the Fourth Amendment. Id. at 1085, 1087.
The beeper used in Knotts revealed no more than could have been learned by visual surveillance. The monitoring of the beeper did, however, enable police to determine the whereabouts of the item to which the beeper was attached after visual surveillance had failed. As to the ability of the officers to recapture the lost contact, the Court observed that “scientific enhancement of this sort raises no constitutional issues which visual surveillance would not also raise.” Id. at 1087.
Knotts teaches us here that monitoring signals from an electronic tracking device that tells officers no more than that a specific aircraft is flying in the public airspace does not violate any reasonable expectation of privacy. Because this is so, no Fourth Amendment violation results from such public detection. The movement of an airplane in the sky, like that of an automobile on a highway, is not something in which a person can claim a reasonable expectation of privacy. As the Eighth Circuit stated in United States v. Bruneau, 594 F.2d 1190 (8th Cir.), cert. denied, 444 U.S. 847, 100 S.Ct. 94, 62 L.Ed.2d 61 (1979):
[W]hat is one’s reasonable, subjective expectation of privacy in the airborne location of an airplane? There can be but one answer: none. Today as our airways become more congested, it is imperative that the location of all airborne planes, of every size and type, be carefully monitored. It is risking collision for an aircraft to surreptitiously venture forth into unassigned air space. For this reason, we do not believe anyone flying an airplane today can reasonably expect that he has a right to keep his flying, landing, or take off location private.
594 F.2d at 1196.2
Knotts deliberately left unanswered not only the question of whether the police conduct that made the monitoring possible violated the Fourth Amendment, but also the question of how such conduct, if illegal, will be dealt with. Butts does challenge the police conduct that made the monitoring of his aircraft possible. In doing so, however, he does not challenge the warrant or its extension. Instead, he bases his motion to suppress on the failure of an officer to carry out the magistrate’s command to re-enter the aircraft on or before August 19 to remove the beeper. The panel majority asserted that this failure to remove the beeper within the period specified by the magistrate tainted the monitoring of the signal and that this taint invokes the exclusionary rule to bar all evidence obtained from tracking the aircraft to its landing site. 710 F.2d at 152. This position is unfounded.
The purpose of the exclusionary rule is to deter improper police conduct that violates a person’s reasonable expectation of privacy under the Fourth Amendment.3 It does not purport to reach all *1518illegal conduct by officers and is not applicable in the circumstances present here.4 The action of the officer in installing the beeper did not result in discovery of any evidence at issue. Both the installation of and the failure to remove the beeper were unknown to Butts; therefore, neither the installation nor the nonremoval could have influenced Butts’s decision to fly the aircraft in the public airspace. The signal from the then unwarranted beeper did nothing more than enhance the customs official’s legal right to observe the aircraft’s public movements. No Fourth Amendment right was infringed.5
No comparable application of the exclusionary rule is found in the precedent of the Supreme Court or this circuit. Cases tracing the taint of illegal police conduct all concern situations in which an effect of the original illegality provokes the defendant to a subsequent surrender of his Fourth Amendment rights or situations in which illegally obtained evidence enables police to collect private facts. For example, if an illegal arrest causes a defendant to give up other incriminating information before the effect of the prior arrest is attenuated, the exclusionary rule applies. See Wong Sun v. United States, 371 U.S. 471, 484-87, 83 S.Ct. 407, 415-17, 9 L.Ed.2d 441 (1963). If officers illegally obtain evidence of criminal conduct and then use that information in an affidavit that causes a warrant to issue for a search or seizure, the ostensibly legal, warranted invasion of privacy falls under the exclusionary rule. See Alderman v. United States, 394 U.S. 165, 176-77, 89 S.Ct. 961, 968-69, 22 L.Ed.2d 176 (1969). However, if following an illegal arrest the defendant commits another criminal act in a public area, an officer who would not have seen the defendant but for the illegal arrest may testify to the criminality he later observes in a public place. The officer may also lawfully seize evidence derived from the commission of the subsequent criminal act. See, e.g., United States v. Bailey, 691 F.2d 1009, 1016-17 (11th Cir.1982), cert. denied, — U.S. -, 103 S.Ct. 2098, 77 L.Ed.2d 306 (1983); United States v. Nooks, 446 F.2d *15191283, 1287-88 (5th Cir.), cert. denied, 404 U.S. 945, 92 S.Ct. 299, 30 L.Ed.2d 261 (1971).
The exclusionary rule does not apply to deter wrongful or neglectful official conduct that does not involve a breach of the Fourth Amendment. See Stone v. Powell, 428 U.S. 465, 486, 96 S.Ct. 3037, 3048, 49 L.Ed.2d 1067 (1976); United States v. Calandra, 414 U.S. 338, 347, 94 S.Ct. 613, 619-20, 38 L.Ed.2d 561 (1974). This is illustrated by the Supreme Court’s latest search and seizure case. In Michigan v. Clifford, — U.S. -, 104 S.Ct. 641, 78 L.Ed.2d 477 (1984), the Court dealt with the admissibility of physical evidence obtained by arson squad investigators who arrived at a burned home well after firefighters, who had extinguished the blaze and departed, and as the house was being boarded up by persons employed by the homeowner’s insurance company. Without a warrant, the arson squad entered the premises. They took possession of three gasoline cans and some pieces of ignition apparatus. The Michigan Court of Appeals excluded all the evidence as the product of illegal activity. Id. at 645. The Supreme Court affirmed the state court’s holding that the arson squad was acting illegally in entering the defendant’s property and searching his home at the time it did without a warrant. Despite the illegality of the arson squad’s presence on defendant’s premises, the Court reversed the exclusion of one of the gasoline cans. This one can had earlier been found in the house by firefighters, but had been removed from the structure and placed in the driveway by a side door. Without detailing whether the can was visible from the public street, the Court held that the defendant’s reasonable expectation of privacy in that can had been lost and that the arson squad could seize it for introduction in evidence. If the arson squad had not gone upon the premises illegally, they could not have taken possession of this can. Despite this “if,” the Court reversed the exclusion of the evidence in which the defendant had no expectation of privacy, calling it “plain view” material both as with regard to its discovery by the firefighters and its subsequent seizure by the arson squad. Id. at 649-50.
REVERSED and REMANDED.
. The government did not challenge the district court’s conclusion that Butts had standing to contest the installation of the beeper. The ph'ysical description of the pilot in the affidavit filed in support of the warrant matched Butts. The *1516district court also found that Butts had possession and control of the aircraft sufficient to confer standing. We do not decide whether Butts had standing to challenge the admission of any incriminating evidence derived from the installation of the beeper because his standing, or lack of it, does not affect the legality of the monitoring of the beeper or the applicability of the exclusionary rule — the only issues we reach today.
. The Supreme Court recently granted certiorari in United States v. Karo, 710 F.2d 1433 (10th Cir.1983), cert. granted, — U.S.-, 104 S.Ct. 972, 79 L.Ed.2d 211 (1984). Karo concerns the warrantless installation and monitoring of a beeper attached to an object that was tracked onto premises where the defendant had a reasonable expectation of privacy. We need not withhold the decision in this case for the resolution of Karo since the surveillance by electronic signal of the interior of a private dwelling in that case is altogether distinguishable from the detection of the public travel identified here.
. Judge Jolly’s dissent emphasizes the deterrent effect of the exclusionary rule. At the same time, it concedes that had the beeper been attached to the aircraft without a warrant, the evidence would be admissible. This necessary concession would encourage an officer to act *1518without securing a warrant to avoid any hazard of exclusion. This reasoning would not only subvert deterrence, but also directly conflict with Supreme Court precedent that prefers "police action taken under a warrant as against searches and seizures without one.” United States v. Ventresca, 380 U.S. 102, 107, 85 S.Ct. 741, 745, 13 L.Ed.2d 684 (1965).
. We deal in this case with a signal device that remained installed for only two days beyond the warrant-permitted period before it was monitored. As did the Supreme Court in Knotts, we pretermit any ruling on worst-case situations that may involve persistent, extended, or unlimited violations of a warrant’s terms. See Knotts, 102 S.Ct. at 1086.
. Judge Goldberg's dissent asserts that even if the actions of the customs officers were not a Fourth Amendment violation, the district court could have excluded the marijuana under its supervisory powers. The district court did not so rule and, in any event, should not have.
All cases in which the use of such power has been approved have required a balancing of competing interests. See United States v. Hasting, — U.S. -, 103 S.Ct. 1974, 1979, 76 L.Ed.2d 96 (1983). Our balancing of interests in today’s case produces a result opposite from Judge Goldberg's.
On the one hand, we have the public deprived of truthful evidence that a smuggler has brought a prohibited substance into the country. In addition, we have the evidence discovered not from any ¡invasion of Butts’s privacy but from detection of his public conduct. Elkins v. United States, 364 U.S. 206, 216, 80 S.Ct. 1437, 1443, 4 L.Ed.2d 1669 (1960), describes the “general need for untrammeled disclosure of competent and relevant evidence in a court of justice.” United States v. Payner, 447 U.S. 727, 736, 100 S.Ct. 2439, 2447, 65 L.Ed.2d 468 (1979), speaks of the resulting detrimental effect of excluding such evidence.
On the other hand, we have proof that for two days past the time limit fixed by the magistrate a legally installed device remained inside an aircraft. We do not know precisely why it was not removed. The dissent describes the non-removal as "blatantly illegal” and "particularly egregious” conduct that evidences "complete disregard for a court order” and "reprehensible scorn for judicial authority.” The record does not support these pejoratives. The installing agent testified he was absent from the area on National Guard duty when the warrant expired. We can know only that the beeper was not removed when the warrant required that it be. For all this record tells us, the presence of the beeper beyond the time limit well could have been due to illness, accident, inadvertence, or bureaucratic bungling.