You could jump out with a parachute
Only if you prefer to be ingested into an engine or cut in half by the tail to auguring into the ground and failing in your mission. (Do you still get 70 virgins if you wimp out at the end?


)
The targets were not that large, even the Pentagon required a controlled terminal dive to ensure a strike (and in actual fact the aircraft came in short). The Twin Towers were only 208 feet wide (that's only 84 feet wider than a 757's wingspan and just 42 feet wider than a 767's), there is no way a commercial autopilot could be set to make that close of a strike until it was WAY too late to even think about escaping. A 757 stalls at 110 knots, so if it is barely staying in the air it will cover four miles in about two minutes. Once you leave the controls, the aircraft is as likely to miss completely and fly on until it runs out of fuel near or over Greenland in the case of the WTC 1 aircraft and somewhere over Columbia for the WTC 2 aircraft or just stall out and wing over, if it does that it will wind up either in the Sound or in the Hudson. The Pentagon aircraft either piles into a parking lot or runs out of fuel over the Atlantic (assuming that someone on board can't produce the greatest feat of piloting in history and manage to bring a heavy commercial aircraft in safely with no training on type).