It's not "scientists" but rather the engineers responsible for the design and manufacture of jet engines.
They will have specified the tolerances underwhich their engines will work reliably.
I think what will have happened is that withthe current situation they will have come under pressure to reassess those tolerances a bit of a case of "Now chaps are you sure you weren't being a bit too conservative?"
Sounds like they've decided to back down a bit.
Let's hope they weren't put under too much pressure eh?
Here's a picture to concentrate the mind
http://dvice.com/asse...umb-550x513-37221.jpg