First of all get as many trucks or small emergency Diesel generators to run as You like, then, with the batteries refilled,
But how to start the generators and charge the batteries? Using solar panels from the nearest building which have ones? Will they provide enough power?
I think there should be some emergency generators in a big airport, but I am not sure, and I don't think they can be hand-started. A hospital definitely has emergency power, but again, I don't think it can be hand-started...
the GPS constellation needs constant calibration to maintain its accuracy, so don't be too quick-draw about that. Might even be a plot point- taking off thinking the GPS is good, only to find yourself hundreds of miles off course when you get to Aus....
An error that great in just several months? Are you sure? Anyway, we know our position on the ground (the airport) and we can check the GPS accuracy. If we cannot re-adjust it (I don't think we can), we can at least keep the error in mind to correct the course.