Row of seats on United Airlines flight comes loose forcing emergency landing at Sea-Tac

A United Airlines flight bound for San Francisco from Seattle-Tacoma International Airport Sunday evening was forced to make an emergency landing after a row of seats gave way during takeoff and slid into the row behind it, injuring one passenger.

The Federal Aviation Administration (FAA) and National Transportation Safety Board are investigating the incident, which authorities called unusual.

United flight 1139 took off as scheduled at 5:20 p.m., said Robin Urbanski, spokeswoman for the airlines. But minutes later, a bolt holding down three occupied seats in Row 3 loosened and the seats slid backward into the three passengers in Row 4. The pilot turned the plane around and returned to the airport.

A 61-year-old woman sitting in Row 4 suffered a knee injury and was transported to Highline Medical Center in Burien, said Perry Cooper, airport spokesman. No other injuries were reported.

An airline maintenance crew discovered the loose bolt on the Boeing 737 and fixed it, said Allen Kinetzer, spokesman for the FAA.

"I've never heard of this [happening]," Kinetzer said.

But given the G-forces at work during takeoff, he said, just one loose bolt is enough to unanchor a row of seats.

The plane was returned to service and headed out for San Francisco at 8:56 p.m.

United is "in the process of compensating the passengers" on the flight, Urbanski said.

The woman who was injured was re-booked on a first-class seat to San Francisco and left this morning, she said.

Sonia Krishnan: 206-515-5546 or skrishnan@seattletimes.com