Incident Overview
On 22 November 2000 at 1020 UTC, a Boeing B757-204 (registration G-BYAN) and a McDonnell Douglas F-15E came into close proximity approximately 5 miles west of the Daventry VOR. The B757 was on a public transport flight from Birmingham to Paphos, Cyprus, with 8 crew and 234 passengers. The F-15E was part of a two-ship training flight from Lakenheath, each with a crew of two. No injuries to any occupants and no damage to either aircraft were reported.
History of the Boeing 757 Flight
The B757 departed Birmingham Airport on a southerly heading and entered cloud between 3,000 and 4,000 feet. Departure control cancelled the Standard Instrument Departure and placed the aircraft under radar control. At FL60, control was handed to Midland Terminal Control (MTC). MTC cleared the B757 to climb to FL90, then to FL100. The controller advised of military traffic at 11 o'clock, one thousand feet above, which the B757 crew acknowledged and saw on TCAS. The cloud prevented visual contact. Shortly after, the commander and first officer suddenly saw an aircraft at their left half-past ten position at very close range and same level. They identified it as a twin-tailed fighter, later confirmed as an F-15. The F-15 passed rapidly across the B757's nose and down the right side. The B757 crew heard the F-15's engines and felt wake turbulence. No evasive action was possible. The crew filed an AIRPROX report and continued to Cyprus.
History of the F-15E Flight
Two F-15Es (two-seat E models) departed Lakenheath about 20 seconds apart in trail formation, with the No. 2 aircraft approximately two miles behind the leader. Only the lead aircraft transmitted a secondary surveillance radar code. They climbed through cloud and leveled at FL100 in visual meteorological conditions (VMC). The flight profile included an aircraft systems check and a change of lead aircraft. When the formation entered instrument meteorological conditions (IMC), the No. 2 aborted the change of lead and dropped back to 1.5 miles trail. The lead aircraft requested a climb to FL110 to regain VMC.
Control was handed to London Military Radar (LJAO). LJAO cleared the F-15s to cross the Daventry Radar Corridor at FL100. Shortly after entering the corridor, the lead requested a climb to FL110. The LJAO controller initially responded to maintain FL100 but then coordinated with MTC via landline and cleared the flight to climb to FL110. The lead began climbing, but the No. 2 did not hear the clearance and remained at FL100. The No. 2 crew noticed on radar that the leader was above them and discussed this. The front seat occupant was vaguely aware of a 'shadow' on his right side. When LJAO asked to confirm both at FL110, the No. 2 climbed rapidly. Later, when advised of the AIRPROX, the front seat occupant associated the shadow with another aircraft; the rear seat occupant saw nothing.
Air Traffic Control Coordination
The Daventry Radar Corridor is 8 nm wide at FL100, centred on the Daventry VOR, in Class A airspace controlled by MTC. Military aircraft are controlled by LJAO, which coordinates corridor use with MTC. Pre-notification is required. For this flight, a printed flight progress strip showing a flight of two F-15s (callsign EAGLE 31) was prepared. At 1003, Lakenheath Departures called LJAO to pre-notify F-15 traffic as BOLAR 31. The LJAO controller confirmed it was the same flight and prepared a handwritten strip but assumed it was a single aircraft and discarded the printed strip showing two. The MTC coordinator agreed to a crossing for a "single F15" at FL100. About two minutes before the incident, LJAO requested a climb to FL110 for the corridor traffic. After coordination, MTC cleared the B757 to FL100 after observing the lead F-15 at FL110 on Mode C. MTC was not advised of the second F-15, and neither controller noticed the primary radar return of the rear F-15, partly obscured by the lead's SSR label.
The No. 2 F-15 did not hear the climb clearance and remained at FL100, resulting in a loss of separation with the B757. Radar data showed the closest point of approach was less than 0.0625 nautical miles.