Interesting letter in today's Irish Independent from an ex Ryanair Training Captain :-
Normal 'mayday' - Letters, Opinion - Independent.ie
Some of the comments below it make interesting reading too!
After the Challenger Shuttle disaster the term "Normalisation of Deviance" was coined with respect to failure of the "O" Rings which caused the catastrophic failure. The deviation from acceptable had become so routine that those involved subconsciously thought this was "normal".
An interesting clip from You Tube here given by one of the shuttle astronauts:-
Longer explanation here:-