> United could provide you an API key to do so via an API, but in practice they won't, only some enterprisey travel software company can get that kind of access, for a steep fee. You could build a tool which automatically puts together an itinerary based on rules and books it, through a tool like this. Perhaps a slightly contrived example but I believe things like this definitely happen.

And you think that's NOT sketchy?

I'm almost afraid to ask where you think the bar is...