A United Airlines plane that departed Friday from San Francisco International Airport was missing an external panel when it landed at its destination in Medford, Oregon.

United released the following statement:

“This afternoon, United flight 433 landed safely at its scheduled destination at Rogue Valley International/Medford Airport. After the aircraft was parked at the gate, it was discovered to be missing an external panel. 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.”

United said the Boeing 737-800 had 139 passengers onboard the plane, with six crew members. The plane also did not declare an emergency while en route to Medford “as there was no indication of the damage during the flight,” United said.

The incident involving United Airlines flight 433 is the latest in a string of recent mechanical problems on United airplanes.

On Thursday, United Airlines flight 1816 took off from Dallas-Fort Worth International Airport at 5:30 a.m. Just before landing in SFO at 7:30 a.m. local time, the United Airbus experienced a hydraulic leak. It was able to land safely, according to officials.

On Mar. 7, a Japan-bound United flight out of SFO was diverted to Los Angeles after a wheel fell off during takeoff.

Then on Mar. 8, in passengers had to be evacuated from a United Airlines plane in Houston after it rolled off a runway during landing and got stuck in the grass.

Also on Mar. 8, a United flight to Mexico City from SFO was diverted to LAX because of a hydraulics issue.

Last Monday, a United flight headed to SFO from Sydney, Australia had to turn around midflight after fluid was seen spewing out from the right rear landing gear.

All of the incidents are now under investigation, and it has some aviation experts questioning their connection to the San Francisco airport.