When a person with a penis offers to pay for the airfare of a person with a vagina, what sort of behavior is implied?

Yes, sex is expected (...and if I know myself, guaranteed). But what I want verified is if paying for airfare is the behavior of a boyfriend/girlfriend? Especially when reimbursement is not required. Is it a booty call or the start of a relationship? Or, because making things complicated is what I do, is the offer of paying for the airfare both a booty call AND the start of a relationship???