I'm a stepmother and a mother, and I know these relationships are difficult sometimes.
This is not about a ride from the airport. This is about the last 2 years and maybe before that. Your husband has a child who doesn't talk to him? What's he doing about it? What has he done for years before it got to this point? What therapist have you engaged to help navigate these years?
On the plus side, he wants to come home. So he didn't contact you - not a huge deal if he's 18. It would be nice, yes, but if he's an adult, he's on his own. By the same token, however, he's an adult, so he doesn't get to tell people to drop everything and come get him (or do anything else).
What I CAN tell you is that this is not your fight. You are his stepmother, period. Your husband has to solve this. Either he works out a livable situation with someone who lives in his house, or the 18 year old adult who wants to make all his own decisions can live on his own where no one expects anything of him.
But, without knowing the whole story, it's really hard to say more.