It was Flt 175, 277,580 pounds at impact, 125,908 kg, going 590 mph, 865 kph, impact energy of 2093 pounds of TNT; do you need that in Joules?
Maybe we should show him the math? Here's the equation for kinetic energy:
KE = ½mv²
That's half the mass in kilograms times the velocity in metres per second squared equals kinetic energy in joules.
American Airlines Flight 11 was a 767-200ER model, which has an empty operating weight of about 82,380 kg. The fuel on board at the time of impact was about 40,000 litres, which has a mass of about 32,160 kg. Adding that to the empty weight of the aircraft gives us 114,540 kg (this ignores the weight of the passengers, crew, and any baggage or cargo, and thus is a conservative estimate). The velocity at impact was about 748 km/h, or 207.8 metres per second. Plugging this into the formula we get:
0.5 * 114,540 * (207.8 * 207.8) = 2,472,437,815 joules.
united Airlines Flight 175 was a 767-200 model, which has an empty operating weight of about 80,130 kg. The fuel on board at the time of the impact was approximately 38,000 litres, which has a mass of about 30,552 kg. Adding that to the empty weight gives us a conservative total mass of roughly 110,682 kg (again, this ignores the weight of the crew, passengers, and any baggage or cargo, and thus is a conservative estimate). The velocity at impact was about 950 km/h. (You have the wrong metric conversion on that, beechnut.) Plugging those values in we get:
0.5 * 110,682 * (263.9 * 263.9) = 3,853,800,347 joules.
The standard conversion factor is that one tonne of TNT is equal to 4,200,000,000 joules. Applying this to our figures for each impact means the first was the equivalent to about 0.589 tonnes of TNT, or 588.7 kg (1,298 lbs), while the second was approximately 0.918 tonnes of TNT, or 917.6 kg (2,023 lbs).
Lastly, let's compare that energy in joules to that delivered by munitions in the U.S. military inventory. A Mk 84 bomb (2,000 lbs/907 kg nominal weight, of which 47% is the high explosives warhead) unleashes roughly 2,164,625,517 joules of energy when detonated. That means the impact of American Airlines 11 was equal to about 1.14 Mk 84 bomb strikes, and United Airlines 175 equal to about 1.78 Mk 84 bombs.