If you are asked for a return ticket in the USA, your US citizenship and/or US address is coming up in the computer and only one ticket. There is no reason for the agent in the DR to ask for a return ticket if you are going to the USA and they are seeing you are a US citizen (not to mention if they glance at the cover of the passport) in the computer.SPIRIT airlines in Orlando asked for it at checkin at their international check in station, which is long walk from their regular check in. Agent entered info from return ticket into her computer. They even asked to see my Dominican eticket. No one in the DR asked for return ticket.