Plane Hijacking

I have no real evidence of this but since the arrests in London I have been thinking(yes thats what the squeaky noises are wheels turning. haha).
If you go back to the 90's and look at some of the plane accidents that happened a few had eyewitnesses that said different things than the offical reports.
Also some of the reports by the ntsb just didn't seem to make total sence to me or others always seemed to be a bit of a cover up. There was the TWA flight that blew up over the Atlantic, there was the flight in Hawaii that the roof opened up as well as many more.
Could some of these been test flights for the terrorist? I wonder if they were possibly trying out differnent chemical cocktails and seat location to get the best and most effective explosion?
Just throwing this thought out there, like I said I have no evidence just a bit of a theory but it does seem possible.

Ive thought about the same regarding TWA flight 800. I feel there is a link to 9/11. I do believe it was blown up with a missile. Whether terrorists or the US navy did it remains to be seen. The investigation was a massive cover-up.