| Cheap Flights: Austin to Saint Croix $213-$249 r/t [February-March] â American Airlines American Airlines has round-trip flights from Austin (AUS) to Saint Croix (STX) for $213-$249 with a connection. Flights February to March. No Weekends. Departures on Monday, Tuesday, Wednesday, and Thursday. Cheapest fares have long connections. A negative COVID PCR test result is required for entry. Click for more details and booking links Cheap Flights: Austin to Saint Croix $213-$249 r/t [February-March] â American Airlines . | 