The National Transportation Safety Board NTSB.L said the ExpressJet flight with 53 people aboard and a single-engine Cessna 172 came within 300 feet of each other over the Gulfport-Biloxi airport last June 19.

Both took off nearly simultaneously from intersecting runways after receiving clearance to do so from the airport tower staffed by Federal Aviation Administration FAA.L controllers, the NTSB said.

"Wow, that was close," the captain of the commuter jet was quoted as saying by his co-pilot, who was flying the plane.

The crew of the ExpressJet Embraer 145 operating as a United/Continental (UAL.N) flight to Houston did not sense a potential conflict even though the two were monitoring radio traffic and acknowledged that the other plane had also been cleared for takeoff from the other runway, NTSB interview transcripts showed.

The crew said their plane's automatic proximity warning system did not sound and there was no need to take evasive action.

The commuter plane flew on to Houston where it landed uneventfully later that afternoon. The Cessna was ordered to go around the airport following takeoff to remove it from any danger.

The safety board documents alleged that the controller in question, who was not identified, had a history of "professional deficiencies" that included non-compliance with standard checklist procedures.

The controllers' union, the National Air Traffic Controllers Association, had no comment on any disciplinary issues but said it took "reports like these very seriously."

The FAA said in a statement it made management changes at Gulfport following the incident and suspended and decertified the controller involved. The controller has since been retrained and is back on the job.

NTSB investigators have made reducing air traffic controller errors and improving runway safety top transportation priorities.

The agency is investigating at least two other cases of potential air traffic mistakes, including one involving first lady Michelle Obama's plane flying near Washington last April.

In the other, two jumbo jets nearly collided on the ground at New York's John F. Kennedy airport last June, according to a Government Accountability Office report in October that said controller errors nearly doubled between 2008 and 2011.

The increase, the GAO said, may be attributable to a changes in FAA policies that encourage reporting mistakes without fear of disciplinary action.

(Reporting By John Crawley; Editing by Philip Barbara)

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