Controllers who knew that a Liberator would be arriving on a path over occupied France
on the morning of 15 February were also reprimanded for not warning the Exeter fighter sector.
The question why the Liberator was not immediately identified on radar screens as a friendly aircraft went unanswered - either its friend-or-foe identification transmitter was not working or it was not switched on.
The flashes of light from the Liberator were assumed to be a Morse-code message flashed from an Aldis lamp. But technically the Liberator should have signalled its friendly status by firing a colour-coded flare.
One of the key lessons learned from the tragedy was that fighter pilots needed better instruction in the recognition of aircraft - both military and civilian.
"In view of the important personages carried in civil aircraft, more attention should be paid to the identification of civil aircraft," the court of inquiry recommended.
The B24 Liberator was to become one of the most familiar heavy bombers operated by US airmen in Europe, but in February 1942 there were not many around.
Stanislaw Brzeski, the first of the Spitfire pilots to shoot, told the inquiry he had never seen a Liberator before
. He mistook it for a German Focke-Wulf 200,
another four-engined aircraft, usually grey in colour.