A United Airlines flight from Chicago-O'Hare (ORD) to Salt Lake City (SLC) was forced to return to Chicago due to a maintenance issue on March 9. According to the Federal Aviation Administration (FAA), there was a possible oil warning light issue. 

United Airlines flight 2137 (UA 2137) operates daily using an Airbus A320 aircraft. UA 2137 flies from Chicago-O'Hare to Salt Lake City in the morning and from Salt Lake City to Newark (EWR) in the evening. The aircraft used for the morning flight on March 9 had registration N421UA. 

Data from FlightAware shows that UA 2137 departed from ORD at 8:59 a.m. and returned to its origin at 11:06 a.m. local time. The 149 passengers and five crew members onboard disembarked at O'Hare and boarded a new aircraft with registration N412UA. The flight departed with the replacement aircraft at 3:20 p.m. and arrived in Salt Lake City at 5:05 p.m. local time. The FAA is currently investigating the incident.

A United representative released this statement when AeroXplorer reached out for a request for comment:

“On Saturday, March 9, United Flight 2137 from O'Hare International Airport to Salt Lake City International Airport returned to O'Hare due to a maintenance issue. The flight landed safely and passengers were deplaned at the gate. Customers departed for Salt Lake City on a new aircraft.”

This is the fifth major incident involving a malfunctioning United Airlines aircraft since March 6. The other incidents were:

• UA 1118, operated with a Boeing 737-800, made an emergency landing at Houston-Intercontinental (IAH) after the left engine burst into flames on March 6.
• UA 35, which uses a Boeing 777-200ER, lost one of its tires shortly after departure from San Francisco (SFO) and diverted to Los Angeles (LAX) on March 7. 
• UA 2477, which used a Boeing 737 MAX 8, veered off the runway upon landing at IAH on March 8.
• UA 821, operated with an Airbus A320, made an emergency landing at LAX after the aircraft experienced a hydraulic system issue on March 8.