WASHINGTON (AP) - Federal officials say there was a close call between a military helicopter and a regional airliner attempting to land at Reagan National Airport near Washington on Friday.

The National Transportation Safety Board is investigating the incident. Spokesman Eric Weiss says that at their closest point, the two aircraft were flying at the same altitude and were only 290 meters apart laterally.

The Federal Aviation Administration says in a statement that the airliner had descended to 120 meters as it approached the airport.

That's when the helicopter, flying lower and ahead of the plane, briefly rose to 120 meters as well.

Weiss said that set off an alarm warning of a potential impending collision aboard the airliner. The airline pilot aborted the landing, circled around and landed safely.