A section of a United Airlines aircraft was discovered missing upon inspection Friday afternoon in Southern Oregon, adding to a growing list of mishaps for the airline.

United Airlines Flight 433 took off from San Francisco and successfully landed 90 minutes later at Rogue Valley International Airport in Medford, Ore., at 11:53 a.m.

Airport personnel noticed a “piece from the underside of the plane,” a Boeing 737-800, was missing upon a routine postflight inspection, Airport Director Amber Judd told The Times.

“Our airport operations were paused briefly so that we could conduct a runway safety check to look for debris,” Judd said. “We did not find anything.”

Judd said the plane landed safely and all 139 passengers and six crew members exited without an issue.

The flight was scheduled to continue to Denver, but was initially delayed 3 hours and 35 minutes before eventually being canceled.

“It’s my understanding that most passengers were aware of the delay and the circumstances, although there were probably some that didn’t know,” Judd said.

United Airlines in a statement Friday said the aircraft’s crew did not declare an emergency to airport personnel as “there was no indication of the damage during flight.”

“After the aircraft was parked at the gate, it was discovered to be missing a panel,” United’s statement read. “We’ll conduct a thorough examination of the plane and perform all needed repairs before it returns to service.”

The airlines also said it would conduct an investigation.

Judd said the plane was an older 737-8 and not one of the Boeing Max aircrafts that have received scrutiny in January after a door panel blew off an Alaska Airlines flight that left Portland, Ore.

Nonetheless, four Boeing planes operated by United have suffered incidents over the last two weeks.

A Boeing spokesperson referred all questions to United Airlines regarding the airline’s fleet and operation.

On Monday, a San Francisco-bound United Airlines flight turned around two hours after leaving Sydney. The Boeing 777-300 aircraft returned due to a maintenance issue.

Prior to that, a Boeing 777-200 operated by United Airlines made an emergency landing in Los Angeles after a tire fell off on March 7.

There was also an emergency landing in Houston on March 4 after flames were spotted coming from a United Airlines Boeing 737-900ER. United confirmed the engine ingested bubble wrap.

Four days later, a Boeing 737-8 Max rolled onto the grass near a runway in Houston upon landing, though no passengers were injured.

United stressed their were no injuries in any of these incidents.

“We take every safety event seriously and will investigate each of the incidents that occurred this month to understand what happened and learn from them,” the United statement said. “Much of this work is conducted together with the manufacturers, the FAA, and the NTSB as well as with the manufacturers of individual components.”