United Airlines flight loses a wheel during take-off in Los Angeles.

A United Airlines jet lost a landing-gear wheel during take-off from Los Angeles, but safely landed at its destination in Denver without any injuries, the airline reported. “The wheel has been recovered in Los Angeles, and we are investigating what caused this event,” United said in a statement on Monday. This marks the second such incident for the airline this year. The aircraft involved in Monday’s incident was a nearly 30-year-old Boeing 757-200, carrying 174 passengers and 7 crew members. Boeing ceased production of the 757 in 2004.

In March, a United Airlines Boeing 777-200 jet bound for Japan lost a tire mid-air after taking off from San Francisco, but landed safely at Los Angeles International Airport. The tire landed on a car in an airport employee parking lot, breaking a window, but no one was injured.

Monday’s incident is the latest in a series of issues involving United Airlines planes. In March, one aircraft was forced to make an emergency landing at Los Angeles International Airport due to a hydraulic system issue. That same month, another flight rolled off the taxiway into the grass while attempting to land in Houston.

Additionally, in March, a United flight 1118, a Boeing 737-900, carrying 167 passengers, made an emergency landing in Houston after bright flames erupted from the engine during its journey from Houston to Fort Myers, Florida.

US flight safety issues were highlighted in January when a door plug blew off an Alaska Airlines Boeing 737 MAX 9 mid-air shortly after taking off from Portland, Oregon, forcing an emergency landing and injuring several people.

In April, United Airlines attributed a $200 million hit to its first-quarter earnings to the incident, stating that the mid-flight blowout on rival Alaska Airlines led to the grounding of many Boeing planes, contributing to the losses.