United and American Airlines have round-trip flights from Phoenix (PHX) to Denver (DEN) for $79-$84, NONSTOP. Flights in May. Departures on Monday, Tuesday, Wednesday, Thursday, and Saturday. Extended weekends available. Origin/Destination reversible.
American is no longer allowing free changes for Basic Economy fares. They still allow free changes for Main Cabin and higher classes. Carry-on bag is allowed for free. You can avoid paying for seat selection by accepting the randomly assigned seat at the gate.
United charges an additional fee for carry-on bags.
Click for more details and booking links Nonstop Flights: Phoenix to/from Denver $79-$84 r/t [May] – American Airlines / United