United and American Airlines have round-trip flights from Houston (IAH) to Tampa (TPA) for $97-$120, NONSTOP or with connections. Flights April to December, but none in June. Origin/Destination reversible.
Note: Carry-on bag is allowed for free on American Airlines, but the route has a connection. You can avoid paying for seat selection by accepting the randomly assigned seat at the gate.
Note: United “Basic Economy” fares are NONSTOP, but 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. If you have the United MileagePlus credit-card, use the “free checked bag” perk.
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).