Corrected entry: At the end of the movie the CIA helicopters are flying from DC to Baltimore. We see them over a wide stretch of water. Then there is a long sequence with McClane, and when we get back to the helicopters they are still over water. When you fly from DC to Baltimore you do not cross a long stretch of water.
Spiritfire
11th Jul 2007
Correction: In the Washington D.C.- Baltimore area there is a "No Fly Zone" that has been in effect since the late 1950's. The most recent edition is the Air Defense Identification Zone (ADIZ) that extends from DC to literally the edge of Baltimore. Woodlawn is on the west side of Baltimore, but because of the radius of the no fly zone, the fastest way to get from DC would be to go east then follow the Chesapeake bay to Baltimore, over water almost the entire trip.
Spiritfire