United has round-trip flights from Houston (IAH) to Cancun (CUN) for $179-$194, NONSTOP. Flights September to December. Origin/Destination reversible.
Note: United “Basic Economy” fares do not include a free carry-on bag. Only a personal item (like a small laptop bag) is free. Seats are randomly assigned for free prior to boarding.
Note: The personal item size on United flights is smaller (9-in/10-in/17-in) than Frontier or Spirit (8-in/14-in/18-in).