Flights to and from Gatwick Airport, southeast England
Incident period: 17 June and 15 July 1991; subsequent official enquiries
Two different Gatwick flights generated unusual-object reports in the summer of 1991. In June, passengers described a wingless projectile below their aircraft. In July, a first officer saw a small black object pass close to a descending Boeing 737. The released records preserve the important differences between the two events, and the detailed search for an explanation of the second.
Two flights, rather than one extended encounter
The June and July reports are often encountered in the same group of released UFO documents. Both involved Boeing 737s associated with Gatwick, but they were separate occurrences. Different people saw different things under different circumstances, and the records should be followed independently.
On 17 June 1991, a Dan-Air Boeing 737-200 was departing Gatwick for Hamburg. Four passengers reported an unfamiliar object below and to the left of the aircraft. No member of the flight-deck crew saw it. Their report entered the Civil Aviation Authority system as occurrence 91/02019X.
On 15 July, the important observation came from the cockpit of an inbound flight. It was treated as an air-miss report, numbered 75/91. That second enquiry generated the more extensive analysis of weather balloons, radar playback and the possibility of a small airborne object.
What the June passengers described
The Dan-Air flight was following its departure route towards the Detling navigation beacon. The passengers described a wingless, projectile-like object below the aircraft on its left, or northerly, side. The paperwork records a sketch as well as their account.
The crew’s estimate placed the object at roughly 4,000–5,000 feet, just above the cloud tops. Because the pilots had not seen it, this was an interpretation of the passengers’ descriptions and the flight’s circumstances. The object’s precise size, speed and direction were not independently measured.
The passengers pressed for the incident to be reported before leaving the aircraft at Hamburg. A handwritten time connected with the destination should not be mistaken for a securely established British sighting time. The date and flight context are firmer than an exact minute reconstructed from that note.
The first investigation’s paper trail
The surviving correspondence shows military air-traffic staff being asked for assistance. Radar photographs from RAF West Drayton were among the material sought. A request for radar evidence is not the same as a surviving radar identification, and the pages examined do not establish a matching military aircraft or projectile.
This makes the June account an unusual passenger report with an official reporting trail. It does not become a multiple-pilot sighting simply because the crew filed the occurrence. The people who observed the object and the people who transmitted their report had different roles.
The surviving papers are useful precisely because they preserve that distinction. They also show why a concise later newspaper account can omit details which matter when comparing cases: who looked out, who did not see it, and which estimates were made after the event.
The July encounter in the cockpit
The 15 July aircraft was descending towards Gatwick at flight level 140, approximately 14,000 feet on the standard pressure setting. Its heading was about 308 degrees and its speed around 355 knots. Visibility was reported as forty kilometres.
The first officer saw a black, lozenge-shaped object approximately five hundred metres ahead at much the same level. It passed on the port side in about a second and a half. The report placed it within a hundred yards and no more than roughly thirty feet above the wing. There was no impact or damage.
The object appeared small: an estimate passed to air traffic control described something around eighteen inches across. The pilot considered a balloon or a detached piece of material among the possibilities. The close passage was the central safety concern; an unfamiliar appearance did not make the object’s composition known.
A radar return which did not settle the identity
A primary radar response was noticed about ten nautical miles behind the aircraft, heading southeast at roughly a hundred knots. Another aircraft was directed to look, but its crew saw nothing. At first glance the radar detail might seem to offer an instrumental confirmation of the black object.
Replay complicated that interpretation. The response behaved more like a low-flying light aircraft or helicopter. It was not established as the small object which had passed the Boeing. The air-miss report therefore did not obtain a single continuous radar-and-visual track of the encounter.
This is an important part of the investigation’s result. A radar response somewhere in the area may be a valid observation in its own right, yet still belong to something else. Joining the two without the replay assessment changes the character of the case.
Checking the obvious balloon candidate
A weather balloon had been launched from Crawley at 17:19. Investigators checked its appearance and ascent, rather than simply accepting the existence of a nearby launch as an answer. The balloon was light brown and associated with mesh, unlike the reported small black lozenge.
By the time of the encounter it was calculated to be at about 27,000 feet, substantially above the descending aircraft. The meteorological analysis also considered whether dark polythene could have risen by solar heating. Conditions included an inversion around 4,000–5,000 feet and a much lower convective ceiling than the aircraft’s level.
Small black balloons used for wind observations offered another possibility, but no particular launch was positively matched. One source checked had not launched such a balloon that day. The investigation thus examined several balloon mechanisms without tracing a definite specimen to the encounter.
The solar-balloon suggestion
A later item in the defence file reproduces an advertisement for a long black solar balloon. A handwritten comment proposed such a toy, possibly carried across from continental Europe, as a likely explanation. It is an intriguing addition because it resembles the general type of small, dark airborne hazard under discussion.
The note is a proposed identification, however, rather than a launch record, recovered balloon or demonstration that the advertised object followed the aircraft’s route. The formal air-miss account had left the object unidentified and recognised a possible collision risk.
Both stages belong in the history. The original technical enquiry explains why a particular weather-balloon launch did not fit. The later annotation shows how a different balloon idea entered the file. Treating either as the whole investigation loses the sequence.
Mapping an airborne case
The UKPX pin marks Gatwick Airport as the common flight reference, not the precise position of either object. The June observation occurred during departure and the July report during an inbound descent. A single airport marker is therefore a browsing aid, rather than a plotted encounter location.
Together, the reports show two routes into the official record: passengers persuading a crew to submit an account, and a pilot reporting a close passage as an aviation hazard. Their value lies in the surviving detail, including the limits of the radar evidence and the practical work done to test possible explanations.
Timeline
17 June 1991: four Dan-Air passengers report a wingless object; the pilots do not see it.
July 1991: military air-traffic staff are asked to assist with the June occurrence.
15 July 1991: an inbound Boeing 737 reports a close passage by a small black object.
Subsequent analysis examines radar playback, weather balloons and small dark balloons; a later file note suggests a solar toy balloon.
Sources & further reading
DEFE 24/1955, PDF pages 98–107 — The June Dan-Air passenger report, occurrence reference, sketch and requests for assistance.
DEFE 24/1963, especially PDF pages 191–193 and 199 — The July air-miss analysis and the later solar-balloon annotation.
Related case files
Alitalia over Kent, 1991: the missile-shaped object and the military enquiries
Manchester Flight 5061, 1995: the wedge-shaped object and the unresolved airmiss report
Location note: Gatwick Airport is the shared flight reference, not the exact location of either airborne observation. The two dates are separate occurrences within this single comparative case file.
UKPX historical case file. Researched and checked 4 November 2026. Explore the UK case map · Links & Sources.