Originally posted by: Shawn
It couldn't have been the jet engine. Because that flight would have taken off regardless of what he did.
In this theory, what I think you're not getting though is that whatever spurred the jet engine through time in the first place, and the creation of the Tangent Universe, will now not happen again. You can't look at it as simply being a linear, single dimension. Since Donnie sent the engine back from the Tangent Universe, when his sister and mother get on the plane, they will not crash this time. The flight will go smoothly and the plane will not crash. They will never discover how and why that engine got there.
