A military Black Hawk helicopter crossed the flight path of a United Airlines aircraft as it approached an airport in California on Tuesday evening, according to the Federal Aviation Administration.

The incident occurred around 8:40 p.m. local time Tuesday, the FAA reported. The United Airlines pilots observed the helicopter in their vicinity and received a traffic alert from their aircraft systems.

In response to the proximity of the military aircraft, the United Airlines pilots leveled their aircraft as a precautionary measure, according to the airline. The maneuver was taken after the flight crew spotted the Black Hawk helicopter crossing in front of their flight path.

The FAA is expected to investigate the circumstances surrounding the incident to determine how the two aircraft came to be in such close proximity during the approach phase of the commercial flight. No injuries were reported in connection with the encounter.

Both the timing and location of the incident suggest it occurred during a critical phase of flight when commercial aircraft are typically following established approach procedures to land at the airport.