| Nonstop Flights: San Antonio or Austin to/from Denver $97 r/t [March-May] â United United has round-trip flights from San Antonio or Austin (SAT/AUS) to Denver (DEN) for $97, NONSTOP. Flights March to May. Weekends available. Origin/Destination reversible. Change fees are waived, but Unitedâs âBasic Economyâ 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. If you have the United MileagePlus credit-card, use the âfree checked bagâ perk. Click for more details and booking links Nonstop Flights: San Antonio or Austin to/from Denver $97 r/t [March-May] â United . | 