I've not been at an airport yet, but my experience tell me they should not be a vector or high-risk place at all. They are quite open, not at all a closed space where viral load builds in the air. Everyone is moving around and you spend little time in close proximity to anyone (hopefully they have addressed lines/crowding at TSA, etc). For the most part you can easily avoid close engagement with anyone. Assuming most or all are wearing face protection, all in all, it seems to be a far less risky proposition than most work environments, indoor restaurants and similar places. Transport to/from parking, or rental car pickup/dropoff, is more risky than the airport itself.