Two separate airliners were forced to abort landings at San Francisco International Airport last week after pilots spotted a Southwest Airlines jet taxiing across runways where planes had been cleared to land.

The close call occurred on May 19, when an inbound United Airlines plane got as low as a few hundred feet over San Francisco Bay, before pilots saw the Southwest jet on the same runway. Pilots of that United plane decided to abort their landing, according to the Associated Press.

Shortly after that, the crew of an incoming Alaska Airlines plane allegedly saw the same Southwest jet crossing a second, parallel runway and aborted their landing.

Audio of the May 19 incident has been released. In it, you can hear the air traffic controller telling the Southwest crew, “You shouldn’t be on the runway,” according to a recording captured by LiveATC.com.

When one of the pilots tried to explain why they were on the runway, the controller cut him off, saying, “I don’t need an argument.”

Both the United and Alaska planes ended up circling around the bay and landing safely.

The Federal Aviation Administration told CBS News the agency looked into the events and determined the appropriate steps were taken to ensure safe operations.