As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GROUNDED: SHORTLY AFTER REACHING FL380, RIGHT PACK MESSAGE ILLUMINATED, AND RESET ATTEMPT AFTER DESCENDING TO FL340 UNSUCSESSFUL. RETURNED BACK TO DFW. NOTED THE RIGHT CAC R1 WORKS ON GROUND WITH APU BUT BECOMES INOPERATIVE WITH THE PACK INOPERATIVE WITH BOTH RIGHT CACS INOPERATIVE IN FLIGHT CLIMBING TO ALTITUDE. **SUPPLEMENTAL INFORMATION: REMOVED AND REPLACED RIGHT AIR CYCLE MACHINE PER AMM 21-52-02 .