ARLINGTON COUNTY, Va. (DC News Now) — The Federal Aviation Administration (FAA) said it was investigating after pilots of a United Airlines flight were forced to abort the plane’s takeoff moments after a regional jet taxied across the same runway.

The incident happened at around 8:30 a.m. on Tuesday, March 7 at Ronald Reagan Washington National Airport (DCA).

An air traffic controller can be heard yelling “United 2003, cancel takeoff clearance!” during the tense moment.

According to the FAA, the pilot of the regional jet — Republic Airways Flight 4736 — was cleared to cross a runway, but taxied through the wrong one.

“The pilot of the Republic flight had originally been cleared to cross Runway 4 but turned on the wrong taxiway,” an FAA spokesperson told DC News Now. “An air traffic controller noticed the situation and immediately canceled the takeoff clearance for the United flight.”

The runway that the Republic Airways flight crossed, Runway 1, is DCA’s busiest. Several hundred flights arrive and depart from Runway 1 every day.

The National Transportation Safety Board (NTSB) was aware of the incident, but hadn’t opened its own investigation. As of March 15, it was unclear how fast the United Airlines flight was in its takeoff roll. Less than two seconds after it was cleared for takeoff, air traffic control ordered the pilots to stop the plane.

The incident follows a cluster of aviation close calls across America that have gotten the attention of safety regulators.

Billy Nolen, the acting head of the FAA, wrote a “call to action” in February, in which he warned “recent events remind us that we must not become complacent. Now is the time to stare into the data and ask hard questions.”

On Wednesday, the FAA hosted an impromptu “safety summit” in McLean, Va. Stakeholders from across the aviation sector met to “examine actions the nation’s aviation community needs to take to maintain its safety record.”