747 Airborne Laser
If you want to weaponize a 747 then checkout the following:
http://www.airforce-technology.com/projects/abl/
They're putting a big chemical oxygen iodine laser (COIL) in a 747-400F and using it as a laser cannon to zap Scud missiles. It occurs to me that a better use for this laser cannon would be to vaporize dictators and mullahs. Imagine some Iranian mullah presenting an open air sermon to the faithful about the satanic Americans. Suddenly out of the blue, there's a bright flash of light and in an instant the evil bastard turns into a cloud of greasy blue smoke. That's a great way to rid the world of scumbags with almost no collateral damage!
Gary