A military helicopter and a regional airliner almost hit each other while they were attempting to land at Reagan National Airport near Washington last week, federal officials said Sunday.

At their closest point, the two aircraft were flying at the same altitude and were only 950 feet apart laterally, said Eric Weiss, a spokesman for the National Transportation Safety Board, which is investigating the incident, according to Yahoo.com.

Republic  Airlines flight 3281 had descended to 400 feet as it approached the airport when thehelicopter, which had been flying lower and ahead of the plane, briefly rose to 400 feet as well, theFederal Aviation Administration said in a statement.

That set off an alarm aboard the airliner warning of a potential impending collision, Weiss said. The airline pilot aborted the landing, circled around and landed safely. The incident occurred at 4:05 p.m. EDT on Friday, Weiss said.

NTSB identified the airliner as an Embraer 175, a twin-engine jet that generally seats about 80 people. The flight originated in Columbus, Ohio, and was destined for Huntsville, Ala., with a stopover in Washington, Weiss said.

Weiss identified the helicopter as a Bell UH-1 based at Joint Base Andrews in Maryland using the call sign Mussel 9. The UH-1, also known as a Huey, has a single engine with a two-bladed main rotor and tail rotor, Yahoo said.

The Air Force's 11th wing, based at Andrews, includes a UH-1 helicopter squadron. Andrews is the military's security base for the Washington area.

The FAA initially identified the helicopter as a UH-60, better known as a Black Hawk, but later confirmed it was actually UH-1.