These are videos of large aircraft at low altitudes:
Low Pass
Hot Dog
So if the planes in the videos were doing 300 mph and drag is proportional to the square of velocity.
300 * 300 = 90,000 500 * 500 = 250,000
250,000/90,000 = 2.8
Going from 300 mph to 500 mph at the same altitude means 2.8 times as much drag. But going from 700 feet to 30,000 feet means 1/4th as much drag.
2.8 * 0.25 = 0.7
So doing 500 mph at 30,000 feet is less drag on the planes than 300 mph at 700 feet. So if the engines were only using 50% of their maximum thrust when cruising at 30,000 feet they could not produce enough thrust to do 500 mph at 700 feet. I think there is a very good chance that ex-Boeing engineer is correct. Since MIT says the plane that hit the south tower was doing 503 mph this makes 9/11 look very weird.
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psikey