Greyhound Bus Lines: Alec Baldwin's a Mean Bully!!!

Greyhound Bus Lines has no idea how they got caught in the crossfire between Alec Baldwin and American Airlines -- but they're not taking it sitting down ... telling TMZ, Alec is woefully ignorant when it comes to bus travel.

In case you haven't been keeping up -- Alec just wrote a diatribe online, blasting American Airlines for kicking him off one of their planes ... calling the whole ordeal a "Greyhound bus experience."

But a rep for the bus company tells us, the actor has no idea what he's talking about -- claiming, "I don’t know if he’s ever been on one of our buses (it doesn’t sound like it), but there are about 17.6 million people who travel with us every year who I’m sure wouldn’t share [his] feelings."