The two pilots in a mid-air collision which killed five people either did not see each other or had no time to take effective avoiding action, an accident report said today.
A contributory factor in the accident was that "insufficient or inaccurate information was provided to the two pilots", the report from the Air Accidents Investigation Branch (AAIB) said.
The flight-landing sequence plan prepared for the flights by the aerodrome controller (ADC) at Coventry Airport was based on an "incomplete understanding" of the nature of the flight of the Cessna light aircraft involved and was "unlikely to have been successful", the report added.
By the time the risk of a collision between the Cessna and the home-built Rand Robinson KR-2 light aircraft was identified, it was "too late to devise an effective method of resolving the situation".
The report said an eyewitness to the collision had said the left wing of the Cessna apparently passed "directly through" the Rand KR-2 which had been built by, and was being flown by, Brian Normington, 70, of Blackdown, near Leamington Spa in Warwickshire.
Mr Normington was killed, as were the two pilots in the Cessna - Sybille Gautrey, 33, from Towcester, Northamptonshire, and Sophie Hastings, 28, from Swadlingcote, Derbyshire.
Two others in the Cessna also died - James Beagley, 34, from High Wycombe, Buckinghamshire, and Harvey Antrobus, 28, from Fillongley, Warwickshire.
The accident happened close to Coventry Airport on the morning of August 17, 2008, with Mr Normington on a private flight and the Cessna on a flight to check navigational aids.
The AAIB said the ADC was not aware of the type of training that the Cessna was undertaking because the flight progress strip, by which air traffic controllers track flights, had incorrect information on it.
Instead of having "ILS (instrument landing system) calibration work" on it, the strip had "IRT" (instrument rating training).
The report said: "Although the crew of G-EYES (the Cessna) explained their intentions on the radio prior to take-off, it appeared that the information was insufficient for the air traffic controllers on duty to understand its full implications."
The report said the ADC believed from the progress strip that the Cessna crew were undertaking instrument rating training and that he did not discover the crew were undertaking ILS calibration training until after the accident.
The report said the ADC had said that, if he had been aware of the true nature of the flight, he might have restricted the number of aircraft in the area around the airport and would have given the Cessna a higher priority for landing.
The AAIB added that, with "a clearer understanding of the nature" of the Cessna flight, the ADC might have developed a different plan. In the event, the plan he did devise was "unlikely to have been successful".
The report said Mr Normington was not informed about the Cessna "approaching on ILS". It added that the sightline to the Rand KR-2 from the Cessna front right seat "probably intersected the canopy behind, or slightly to the left of, the windscreen central pillar".