07:10 AM EDT, 03/18/2024 (MT Newswires) -- The US Federal Aviation Administration has launched investigations over three incidents involving Boeing 737 planes in the US over the weekend.

In the most serious, an external panel blew off a United Airlines (UAL) Boeing ( BA ) 737 mid-flight on Friday.

The plane, United Airlines Flight 433, landed in Medford, Oregon after departing from San Francisco. "A post-landing airline inspection revealed a missing panel," the FAA's statement said.

According to a statement cited by Reuters, United Airlines said it will conduct a "thorough examination" of the plane before it returns to flight.

Also on Friday, an American Airlines Boeing 737-800 landed safely in Boston around 1:50 p.m. local time on March 15, after the crew reported a problem with the flap. The plane was traveling from Dallas-Forth Worth.

In another incident Sunday, a United Airlines Boeing 737-800 landed safely in Chicago after the crew reported a problem with "air data indication" on the plane during a flight from New York, the FAA said. The incident is also under investigation.

Boeing ( BA ) shares fell 1% in premarket trading.