Okay, being an AE student, I must pose a conundrum of sorts.
First, a new term: Factor of Safety. The factor of safety is a ratio of the ultimate stress a building material can take, divided by the largest load that material will be undergoing during normal operations.
For a building, FoS is typically about 7~9. That is, a building that is built to withstand 30,000 pounds of force, should be able to take about a quarter of a million pounds of force before it crumbles.
Now, not to scare you or anything, but the FAA mandates that aircraft be built with a FoS of 1.5. And wanting to make aircraft as cheap as possible, manufacturers will try to get as close to it as possible, without going under.
So, take a 757, with a FoS of 1.5 and ram it into a building with a FoS of 9. Sure, the 757 will do some damage, going at 500~600 mph, but there isn't going to be much of the aircraft left.
To reiterate, a building that is designed to take 10,000 lbs of force, will not collapse before a force of almost 100,000 lbs is reached. An airplane built for 10,000 lbs of force, will break at a little more than 15,000 lbs. of force.
Now, which do you think will win in a collision? The airplane, or the building?
And information cover ups? It's the DoD. What do you expect? They still have people thinking there's UFOs in New Mexico...