They say the computer systems outage affected its website and airport computer systems around the country.
Airline spokeswoman Tina Swail says some computer systems were back online by Friday evening and the carrier was "working to restore operational order."
Swail didn't have any have information on when the outage occurred or what caused it.
Officials at Phoenix Sky Harbor International Airport say the power outage led to long lines at ticket counters.
They say the outage happened in mid-afternoon and passengers couldn't make reservations, check in online, change their flights or check flight status.
