Southwest, FedEx Planes Came Within a Thousand Feet in Austin on Saturday

Shortly before that aircraft was set to touch down, an air-traffic controller cleared a Southwest flight to depart from the same runway, he said.

The pilot for the FedEx flight stopped landing procedures and proceeded to climb, the FAA spokesman said. The Southwest jetliner, a Boeing 737, was able to take off safely.

Flightradar24, an aviation-tracking service, released an animation of the incident that showed the Southwest aircraft starting to roll down the runway for liftoff. Soon after, the FedEx cargo jet moves toward the runway behind it. 

In an audio recording of communications from an air-traffic control facility, a controller can be heard clearing the Southwest crew to take off and advising them that a 767—the FedEx plane—was 3 miles behind in its approach. A controller later asks Southwest to confirm that it was rolling for takeoff. 

“Southwest abort. FedEx is on the go,” someone later says on audio from the air-traffic control facility.

The FedEx plane at one point reported an altitude of 75 feet but began to climb as it caught up with the Southwest plane, according to the animation. At one point, it was less than one thousand feet away from Southwest’s jet, a Flightradar24 spokesman said. 

The National Transportation Safety Board is initially sending two investigators to Austin to look into what happened, a spokesman for the NTSB said Sunday. A preliminary report about the incident from the safety board may be available in 15 days, he said. The FAA is also investigating the incident.

A spokeswoman for Southwest declined to comment and referred questions to the FAA. The FedEx plane landed safely at the Austin airport following the event, a FedEx spokeswoman said, directing questions to the FAA and the NTSB.

Aviation-safety regulators have raised concerns about the potential for collisions on runways and taxiways in recent years and have adopted new systems aimed at reducing close calls between planes on runways.

Aviation-safety authorities are also investigating another near-collision on a runway at John F. Kennedy International airport last month.

In that situation, a Delta Air Lines Inc. flight was headed down the runway for takeoff when air-traffic controllers noticed another plane crossing the departing jetliner’s path, the FAA said at the time. Delta’s pilots aborted their takeoff and safely came to a stop about 1,000 feet before reaching the point where a Boeing 777 operated by American Airlines Group Inc. was crossing, according to the FAA’s preliminary analysis.

The American pilots had been given permission to cross a different runway from the one Delta was using to take off, but proceeded across the incorrect runway, according to recordings of air-traffic control communications from the event, and a preliminary FAA summary of the incident reviewed by The Wall Street Journal.

Write to Micah Maidenberg at micah.maidenberg@wsj.com and Alison Sider at alison.sider@wsj.com