Plot hole: Hogan has the men fly kites to get wind data and build a hot air balloon for a man to escape in. In reality, kites and hot air balloons are pretty much mutually exclusive - if there's enough wind to fly kites, one can't launch a hot air balloon, and vice versa.Doc
Continuity mistake: When the British spy is trying to get to the camp, the area around him seems fairly lit, as at dusk, after the sun just set. When he glances toward the gates, the sky is black, suggesting night (the shot of the gate is stock footage). When the shot goes back to the spy, it's dusk again.