I get the feeling that people who did this movie and the second Die Hard are completely ignorant about DC and the surrounding vicinity. There are two major airbases in that vicinity - Andrews and Langley. This limits the possibility of an attacking plane to hitting the WH to nil in this post-911 world.
Passenger planes fly right close to downtown DC all the time; I'm sure they'll have some handwave line about how they fooled/hacked National Airport into thinking they were legit. Either that, or they remotely disabled all military aircraft... with hacking
. It really wouldn't be more egregious than some of the stuff Skyfall
threw at us, and that
movie's been fairly well received.