Personally, I see it as a case of DM railroading leaving few options open to the player.
Personally, I'd also want to get back to the airport. I may not be able to pilot a plane to fly out of there, but as the OP says, lots of food, large vehicles, large open spaces from which to see walkers, diesel fuel (gasoline goes bad), probably generators, welding equipment, tools, and if there is ever a government/military response, the first thing they will secure is airports to facilitate safe logistical transport of food and weapons.
Going out on the highway to find survivors is about the dumbest thing I've ever heard of. You don't do that kind of thing until after you have a secured location to fall back upon. It's the kind of dumb garbage the Dale character in the show/comic would do that generally screws the group at every turn.
Finding survivors should be the LAST goal of a survivor group. More mouths to feed, more ppl to protect, more ppl to cause group indecision.
Their first goals should be the 3 Ws, Warmth, Water, and Weapons. After that, finding food and securing their position.