One major error (spoiler)
While I feel most of the movie is plausible, the problem I have with the ending is that all communications were on the primary National Guard frequency. You'd think a 'secret' mission would be on scramble or at least a frequency that isn't monitored by every military unit! Also if they were ordered to ignore and make no contact wouldn't it just be easier to turn the radio off or go to a secondary?
I may be wrong on it being Guard, but I thought that's what I heard. But still appears to be a common channel.