My pessimistic advice is that the best Japanese to use in an airport is English.

That's right. Stewards may smile at you while you try to speak their language, but if they reply back in Japanese and you don't understand, they're going to get upset very quickly. Too many passengers try to communicate in a language they don't really master and now isn't the time to have casual conversation, they're working. Same thing with most Japanese people at touristic places. You may slow them down. They're trained for their job, they're not language assistants or Japanese teachers.

That being said, if you're at an N3 level with speaking I guess you'd be able to talk with them. I'm just giving a general life advice.