Title seems unrelated to Hacker News but this is a wonderful break down of the differences between standard airlines and low fare.
I can't speak for Europe, but in the United States, we have the FAA that pretty much dictates how safe the planes are. Flying a "discount" airline couldn't be any less safe than flying one of the majors because the FAA is dictating how they take care of the planes.
Compare this with KLM (worst accident ever), BA, Air France etc. And bear in mind that budget carriers operate the most 'dangerous' routes, short hop frequent take-off landing all weather - not the 'safest' transpacific long haul routes.