From recollection, ATC had cleared two or three flights to leave before the ramp was closed. Two of these opted for deicing. One, (a Porter Airlines Dash 8 bound for Toronto) elected to forgo deicing.
I think Air Force 1 got stuck behind either one or both of the planes that had been deiced.
ATC had been advised that there would be an hour freeze on any activity, starting at about 5:10 local time, while the President was on airport property.
As it turned out, this freeze was lifted within 5 - 7 min. after his departure, according to ATC, although this info didn't seem to get to operations for another 5 - 7 min. from what I could gather from their transmissions. Pilots were calling in for requests for instructions as there was some kind of red light signal on the ramp that had to be extinguished in order for the pilots to be able to push back.
The departure actually went a lot smoother than the arrival. During arrival, there must have been 7 to 10 flights that were left on the apron unable to access their gates as the President was on the property.