Vixen
Penultimate Amazing
Because in the Cold War the world was a very different place.
Sweden was supposed to be a neutral 'non-aligned' country.
It was operating secret, sigint recon flights using top secret British electronics.
Russia denied shooting the aircraft down and Sweden denied they were spy flights.
It was classified and secret from the start. It was genuine spy stuff.
It happened quite often in the Cold War, a lot of incidents were reported as accidents at the time and are still classified.
That does not excuse their failing to inform the men's families they had died in action, instead of giving them false hope they might still be alive in a gulag. It was the Russians who declassified it. The Swedish airmen were not even over Russian waters.