An American Airlines Boeing 737-800, registration N315PE performing flight AA-884 from Dallas Ft. Worth,TX to Denver,CO (USA), was climbing out of Dallas' runway 18L when the crew requested to level off at 9000 feet reporting flight instruments disagreed, subsequently explaining both airspeed and altitude disagreed. The crew reported they were level at 9000 feet, ATC confirmed that he was showing them at 9000 feet, too. The aircraft returned to Dallas Ft. Worth for a safe landing on runway 17R about 20 minutes after departure.
A replacement Boeing 737-800 registration N921NN reached Denver with a delay of 2 hours.
The occurrence aircraft is still on the ground in Dallas about 23 hours after landing back.