Yeh, whiteboard works but another more technical solution could be roll out a TV stand and hook up the TV to a laptop via HDMI and update schedule live through a shared doc (Google docs?). I mean, whatever works right...
They'll stare at the blank screens and wonder what's happening. A whiteboard in front of those screens, and other hot-spots, is far more considerate of how people behave inside a departure lounge.
Low-tech solutions to high-tech problems can be quite beautiful when executed well. It's a sign of good contingency planning because they anticipated no network availability, rather than betting on network redundancy.
I hope the few people who missed their flights were compensated in some way (refunds, seats on the next available flight...).
Not many companies have 10 spare people on site ready to act as emergency whiteboardmen.