But a researcher at Massachusetts Institute of Technology, by closely studying videos of the attack, has estimated the planes' speeds.
But the difference in the towers' survival times, which translated into a difference in the amount of time tenants and rescue personnel had to get out, could be related in part to the planes' speeds, researchers said.
Medevac planes sped him homeward for advanced surgery.
"The noise I heard was long, like eight seconds, as if the plane was going more slowly than military plane speed.
As unscientific as that conclusion may be, it does demonstrate one speed bump facing any assessment of the state of manners on American highways: while it may be easy to discern what constitutes rude behavior in an airport or on a plane, speed limits, along with a lot of unwritten traffic laws, vary not by state but by driver.
Ryan Burch The 22-year-old pro surfer and shaper is fast gaining recognition for his ingenious D.I.Y. boards (related video) - particularly his rectangular, finless, un-glassed foam plank, the Lord Board, which minimizes drag and optimizes planing speed - and for his ability to ride boards of almost any shape and size with grace (bobbersandsinkers.tumblr.com).tumblr.com
Propeller guards were ineffective at planing speed and only slightly helpful at idle speed.
Since the flare location was at W70, the sky-plane speed needs to be close to the true speed.
Deprojecting the sky-plane speed (1,466 km/s), we estimated the peak speed as 1,560 km/s, suggesting that this was a slower event.
The in-plane speed of propagation of the reaction was experimentally determined using a time of- flight technique.
