JetBlue has round-trip flights from Austin (AUS) to Orlando (MCO) for $137, NONSTOP. Flights August to February. Very few weekends available. Origin/Destination reversible.
Note: Weekend availability has very few seats.
Note: Carry-on bag is allowed for free on JetBlue. You can avoid paying for seat selection by accepting the randomly assigned seat at the gate.
Note: Frontier/Spirit/United have slightly cheaper fares, but they will be more expensive over-all because they charge a fee for both checked and carry-on bag.