> why, oh why does every airport need its own proprietary one?

I can understand that. It sure sounds like transportation in general might benefit from some sort of a unified API world-over. This would make every airline/airport share the same kinds of information in the same ways.

I agree with your sentiment that one app should be all you need.

Extending this to other forms of transportation would be great. Just not sure how something like that would be accomplished.

That said, they (airports, etc.) could not rely on apps to communicate with passengers because you can't assume everyone will have access to them.