If I had to pick a cause, I would say either pilot error (clipped a building on take off), mechanical error, or both. Early reports say the pilot couldn't get the landing gear to retract. It is very likely the cockpit crew was distracted and did not have enough rate of climb to clear the obstacles @ the end of the runway. Other factors could be poor crew training and poor maintenance. The aircraft was a former American Airlines machine, like I said in my earlier post. N862AA (its American Airlines registry) was first delivered to American Airlines in December 1963 so the aircraft was 40 years old.