Ralph here believes that Flight 175 (the second plane to hit the towers) would not have been able to achieve it's reported 500 knot impact speed without significant modifications to the airframe and engines.
... so an un-named power develops a nefarious plot to fly an airliner into a building, and instead of simply using a normal airframe and 300 odd knots, decides to re-develop the airframe simply in order to achieve a slightly (in terms of damage done) impact speed of 500 knots?
