QuietQT

From what I've read, it's an issue with fuel weight being too much or something. It was supposed to be fixed by the F-15E launch, but apparently that came sooner than they had anticipated and so it wasn't ready by then. That's my vague understanding from their discord. Edit, through more reading it IS also an engine issue, but again they know about it and should be in an upcoming update

It's a know issue I think they said it should be fixed in the next open beta update.