PORTLAND, Ore. (AP) — A Boeing 737-800 was found to have a missing panel after a United Airlines flight arrived at its destination in southern Oregon on Friday, airport officials said.

United Flight 433 left San Francisco at 10:20 a.m. and landed at Rogue Valley International-Medford Airport in Medford shortly before noon, according to FlightAware. The airport’s director, Amber Judd, said the plane landed safely without incident and the external panel was discovered missing during a post-flight inspection.

The airport paused operations to check the runway and airfield for debris, Judd said, and no debris was found.

Judd said she believed the United ground crew or pilots doing routine inspection before the next flight were the ones who noticed the missing panel.

The panel was on the underside of the aircraft, where the wing meets the body and near where the landing gear deploys, United told The Associated Press via email.

Via email, Boeing deferred comment to United about its fleet and operations. The message included a link to information about the airplane that was involved, and it was said to be more than 25 years old.

There have been several incidents involving Boeing aircraft in recent months.

In January a panel that plugged a space left for an extra emergency door blew off a Max 9 jet in midair just minutes after an Alaska Airlines flight took off from Portland, leaving a gaping hole and forcing pilots to make an emergency landing. There were no serious injuries.

The door plug was eventually found in the backyard of a high school physics teacher in southwest Portland, along with other debris from the flight scattered nearby. The Department of Justice has launched a criminal investigation.

On March 6, fumes detected in the cabin of a Boeing 737-800 Alaska Airlines flight destined for Phoenix caused pilots to head back to the Portland airport.

The Port of Portland said passengers and crew noticed the fumes and the flight landed safely. Seven people including passengers and crew requested medical evaluations, but no one was hospitalized, port officials said.