The lighting outage Friday night affected 16 flights at Tucson International Airport.

Mamta Popat / Arizona Daily Star 2016

A power outage that shut off runway lights and affected more than 15 flights at Tucson International Airport Friday night was caused by a construction mishap, the Tucson Airport Authority said Monday.

The outage occurred at about 7:30 p.m. Friday and power wasn’t restored until about 10 p.m.

Fifteen incoming flights were affected, including five diverted to Phoenix before taking off and landing in Tucson, and one outbound flight was delayed, airport officials said.

The lights on a secondary runway in use at the time went out when a metal part on an underground circuit box was dislodged during nighttime runway repaving operations on TIA’s main runway, Tucson Airport Authority spokeswoman Jessie Butler said.

Because TIA’s main runway was being repaved, flight operations were being conducted on the airport’s crosswind runway, known as 3/21 for its compass bearings.

“While they were repaving, it dislodged a handhold and it got into the power cable and damaged the electrical circuits that supported the lights on runway 3/21, which was the runway that was in use at the time,” Butler said.

The airport has backup generators, but the location of the cable outage on the aging power loop that serves the runway lights prevented their immediate use, Butler said

Airport officials determined it would be quicker to finish up some minor paving work on the main runway and reopen it, though it took some time to move construction equipment and workers and to inspect the runway for debris before opening it, she said.

“So it doesn’t happen again, for the immediate future construction crews have adopted new procedures for paving that should eliminate that issue from happening,” Butler said.

Longer-term, additional redundant power sources are included in a larger airfield safety enhancement project, now in the planning stages, she added.

Airports are supposed to have backup power systems for their airfield lighting systems that kick in automatically within seconds of an outage of a primary power source, according to Federal Aviation Administration rules.

FAA spokesman Allen Kenitzer said the agency is aware of the TIA outage and is looking into it, referring other questions to Tucson airport officials.

One scheduled Friday evening departure from TIA, a Southwest Airlines flight to Las Vegas, was delayed during the outage before eventually taking off, Butler said.

American Airlines canceled one flight from Phoenix, and a United Airlines flight that was diverted to Phoenix arrived in Tucson the next morning, Butler said.

Contact senior reporter David Wichner at dwichner@tucson.com or 573-4181. On Twitter: @dwichner. On Facebook: Facebook.com/DailyStarBiz

Senior reporter covering business and technology for the Arizona Daily Star/Tucson.com