Transportation Security Administration spokesman Jon Allen says an officer discovered about 4:30 a.m. Saturday that an exit from one of the terminals was unguarded.
He says three checkpoints were closed and officers reviewed videotape from all three exits.
Allen says the tapes showed no one entered the secure area through the exit while it was unguarded.
Airport spokesman Marshal Lowe says all terminals are now open. He says five arrivals and three departures were slightly delayed.
Allen says the TSA is reviewing how long the lane was left unattended. He says the incident will be investigated.