On Friday 2 April 1982 The Falklands War began between Argentina and the United Kingdom. On the 4th of May a Super Etendard belonging to the Argentine Navy launched a AM39 Exocet missile into the HMS Sheffield.
After the ship was hit by the missile, the crew had to abandon the HMS Sheffield. While they were waiting to be rescued, Sub Lieutenant Carrington-Wood sensing an abrupt drop of morale, started singing “Always Look on the Bright Side of Life”.
That was the song from a famous British comedy Life of Brian, released in 1979. The scene where it was performed shows Brian who is left to be crucified, and a soon-to-be-dead Eric Idle who played Bryan, starts singing a song about always looking on the bright side of life.
This turns out to have become a tradition among British troops.
A month later the British ship HMS Coventry was badly damaged and sunk in a bomber attack. While waiting in the water to be rescued and watching their ship fall to the depths, the crew started singing ironic song to cheer themselves up.
A decade later, in 1991 During the Gulf War, the tradition still didn’t die out. British Tornado bombers flew on some of the most dangerous low-level missions against Iraqi troops. During this bombing runs they were facing strong anti-aircraft fire. As their brothers in arms from Royal Navy, pilots flying on these missions used to sing “Always Look on the Bright Side of Life”.
Sources:
http://en.wikipedia.org/wiki/HMS_Sheffield_(D80)
https://en.wikipedia.org/wiki/Falklands_War