PHOENIX -- A power outage of nearly an hour at Sky Harbor Airport forced the airport to use backup generators Thursday morning.
The outage affected Terminal Four's D concourse and 32nd to 40th streets and Washington Street to Sky Harbor Boulevard.
Utility company Arizona Public Service originally did not know how long the power would be out nor what caused it, but gates were operating normally by around 11 a.m.
The outage caused dozen of Southwest Airlines flight delays.
One traveler tweeted there was smoke in the building.
Partial power outage in D concourse of Terminal 4. Backup power is operating. Use A or C Checkpoint as alternative. APS on the way.— PHX Sky Harbor (@PHXSkyHarbor) May 22, 2014
During the outage, passengers were screened at three Terminal 4 security checkpoints not affected by the outage.
Meanwhile, stairs were used to take passengers off some flights when jet bridges wouldn't work during the outage. Those passengers were then escorted into the terminal.
The Associated Press contributed to this report.