When I saw that slow moving Hercules, as compared to a fighter plane, approach DC, I thought, where are the fighters?
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.
I am curious, why didn't the film makers go for a different time setting and base on a potential scenario that happened in the past. For example, the US is involved in a second Civil War - a scenario explored in science fiction - and the WH is threatened by an advancing military force hell bent on capturing the president. Then, show the good guys getting the president out of the WH to safety, or defending the WH successfully defending the WH against attack. (The possibility of the WH and the president being attacked were real concerns in the first Civil War. However, the South blundered, lost two battles, and had to retreat quickly back to Virginia.)
I am not buying the concept behind either film. DC has been turned into a quasi-fortress after 9-11; there is no way that a North Korean military force or a paramilitary unit would be able to breach this fortress.