The Airbus that hit Queens in November 2001 killed everybody on board but, again, only 5 on the ground.
Even if the plane and all its contents and passengers were shredded into shrapnel, most of the pieces would reach a terminal velocity of less than lethal force before hitting anybody on the ground.
That may be true, but their intention was obviously to kill lots of people on the ground. Furthermore, with better targeting - over a business district, say, or even when landing at the airport - they'd take out a lot more people than a non-targeted crash over a residential neighborhood of single-family houses where most people were not even home at the time.
That's not what they were hoping for in an airburst. They want cameras. Some kind of video showing the plane gliding over the city and then bursting into flames, something that will immortalize their attack the same way the cameras of 9/11 did. That would magnify the effects of terror far more than any body count.