A United Airlines flight is missing an exterior panel after it landed safely in Oregon

(CNN) — A United Airlines flight discovered that an exterior panel was missing from the aircraft after it landed in Medford, Oregon this Friday afternoon after taking off from San Francisco, California.

The plane, carrying 145 passengers and crew, had landed safely and was parked at a gate at Medford Rogue Valley International Airport when a person on the ground first noticed the panel was missing, United Airlines said in a statement.

The crew of Flight 433 did not declare an emergency and there were no signs of damage during the flight, according to the airline.

According to United, the aircraft is a Boeing 737-800. It is of an older generation and not the new 737 Max aircraft that has been making headlines lately.

United said the missing panel did not affect the plane’s flight characteristics.

United spokeswoman Leslie Scott told CNN that the missing panel was under the fuselage, under the wing and behind the main landing gear.

Amber Judd, director of the Medford Rogue Valley International Airport, told the Rogue Valley Times that the aircraft was not airworthy and “will be here for a while.” Judd added that it is unclear where the missing panel is.

“They don’t know where they lost it,” Judd told RV Times.

United said it would “thoroughly inspect the aircraft and make any necessary repairs before it is returned to service.”

“We will also conduct an investigation to better understand how this damage occurred,” the airline added.

The Federal Aviation Administration said it would investigate the incident.

Operations at the Oregon airport were halted while a runway safety review was conducted after the flight landed safely around noon, Judd told CNN in a statement. “After no debris was found at the airfield, normal operations at the MFR resumed a few minutes later,” Judd added.

The discovery of the missing panel comes as United faces investigations into a series of incidents involving various aircraft, including an engine that ingested bubble wrap and caught fire mid-flight and another flight that lost a tire after takeoff.