WASHINGTON >> The National Transportation Safety Board will hold a June 6 hearing to determine the probable cause of a February 2023 near-miss incident involving a FedEx cargo plane and a Southwest Airlines jet in Austin, Texas.

The two planes nearly collided when the FedEx Boeing 767 was forced to fly over the Southwest jet to avoid a crash in poor visibility conditions. It was one of at least half a dozen near-miss incidents last year that raised concerns about U.S. aviation safety and the strain on understaffed air traffic control.

NTSB Chair Jennifer Homendy said last year the planes came within about 115 feet (35 meters) of each other in what could have been a “terrible tragedy.” The FedEx plane’s first officer saw a single light in the fog from the Southwest Boeing 737-700 and then the plane’s silhouette before the crew aborted their planned landing on the same runway, Homendy said.

An air traffic controller had cleared both planes to use the same runway. He told the NTSB in an interview released last year he had assumed the Southwest plane would have already departed before the FedEx plane landed given his “expectation bias” that Southwest planes were quick to depart.

Homendy said last year the FedEx plane flew over the Southwest aircraft during their takeoff roll momentarily and then the Southwest jet passed beneath the FedEx plane as its speed increased on takeoff.

The Cancun, Mexico-bound Southwest flight, with 123 passengers and five crew aboard, safely departed. There were three crew members on the FedEx plane.

The Federal Aviation Administration has vowed to boost air traffic control staffing. The FAA said on Wednesday it agreed to delay implementation of new mandatory rest periods after discussions with the controllers’ union.