A United Airlines passenger jet grounded at the Medford airport Friday after a post-landing inspection flagged a missing underside panel remained in Southern Oregon on Saturday, and a scheduled no-passenger Sunday ferry flight to Denver has been canceled.

United Flight 433 arrived in Medford from San Francisco at 11:53 a.m. Friday, according to online flight tracking apps. Earlier Friday, the Boeing 737-824 aircraft had flown from Nashville to San Francisco. It was scheduled to fly to Denver later Friday afternoon.

Jackson County Airport Director Amber Judd said Friday no injuries were reported. She said the aircraft “will be here for a while,” and United officials said Friday an investigation would be conducted.

Multiple online flight-tracking apps Saturday indicated the plane — N26226 — was initially scheduled to leave Medford Sunday around 10 a.m. for the no-passenger flight to United’s Denver hub. However, flight trackers later showed the departure was canceled.

The plane was not a new aircraft. Judd said that newer model aircraft — such as the Alaska Airlines Boeing 737-MAX 9 that lost a passenger compartment side panel mid-flight near Portland in January — do not fly in Medford.

“It was not a MAX aircraft,” Judd said.

According to the aircraft’s N-number, the plane was delivered to Continental Airlines on Dec. 22, 1998. It has been operated by United Airlines since Nov. 30, 2011.

Flight 433 landed safely, and the Medford airport was the scheduled destination, according to an email Friday from United Airlines’ media relations team. The flight was carrying 139 passengers and six crew.

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

“We’ll also conduct an investigation to better understand how this damage occurred,” the statement added.

There was no indication of the damage during the flight, according to United.

The whereabouts of the missing metal piece is unknown. “They don’t know where they lost it,” said Judd, the airport director.

The search for the missing part prompted airport officials to temporarily close two runways Friday. Judd said it lasted “just a matter of a few minutes, maybe 15 minutes” while crews ensured there was no debris.

“Then the other planes started landing and taking off,” Judd said.

Four Boeing planes operated by United have suffered incidents over the past two weeks, the Los Angeles Times reported.

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, according to the L.A. Times.

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, the newspaper reported.

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, according to the L.A. Times.

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