The crash of an American Airlines flight in Washington, DC, has renewed anxiety about air-traffic control staffing and procedures at US airports, especially in crowded airspaces.
As investigators began to piece together how a military helicopter collided with the regional jet, questions swirled about communication between the pilots and Reagan National Airport's control tower.
Sen. Tammy Duckworth, an ex-Army Black Hawk helicopter pilot, told reporters that military aircraft usually do not talk directly to commercial pilots, as ATC is the responsible intermediary.
"Everybody's listening on the same frequency," she said, adding that the American flight that crashed would have been aware of the Black Hawk helicopter in the skies. "You are listening to instructions from ATC. ATC is telling you what to do."
Duckworth said an FAA briefing involving ATC tapes revealed the helicopter pilots were told about the passenger plane, and the crew confirmed "at least twice" that they had the jet in sight before the crash.
She added that the American flight was cleared to land and would have had the "right of way" and that the Black Hawk was told to pass behind. The flight was in visual flight conditions, meaning the helicopter would be visually searching for the plane.
"They would be looking up to try to find this aircraft, pick it out of the sky as it's coming in for a landing," she said.
According to the Federal Aviation Administration, some military and civil aircraft, if equipped, can talk to each other using specific emergency frequencies. This is usually reserved for distress situations where immediate communication is necessary. It's unclear if the Black Hawk was equipped.
"[The Black Hawk's] flight path should have been hugging the east bank of the Potomac River, so they should not have been within the flight path of that landing aircraft," she said. "Did one of the aircraft stray away latitude, sideways in the airspace from the route that they were supposed to be on?"
National Transportation Safety Board member Todd Inman said the DC area is a unique environment for helicopters and that the Black Hawk was transitioning zones at the time of the crash. ATC is one of the "human factors" the agency will examine as part of its investigation, he said.
Air traffic control is a complex system with many moving parts and no room for errors
The national air traffic system in the US is immense in both size and complexity, 14,000 air traffic controllers handle upwards of 45,000 flights a day across 29 million miles of airspace.
It's an intricate network that includes hundreds of regional and area control centers, each responsible for a specific piece of airspace.
A pilot flying from San Francisco to Washington, DC, for example, could interact with more than 20 different controllers during the flight.
The job is infamous for its high stress and heavy workload, which can involve managing upwards of a dozen flights at a time.
These stressors are amplified for airports like Ronald Reagan National. The airport has strict flight paths and altitude restrictions. It handles more than 25 million passengers a year and is located in highly trafficked and highly controlled airspace, as it is near the White House, Pentagon, and other government buildings.
The airport has seen multiple near misses recently, including a Southwest Airlines flight that was instructed to cross the same runway on which a JetBlue plane was starting its take-off.
A month later, an American Airlines flight was cleared for takeoff at the same time another plane was given the go-ahead to land on an intersecting runway.
Controllers working the airspace in and around Reagan National also have to handle an extraordinary amount of private and military aircraft that operate in the area.
The situation is exacerbated by a shortage of around 3,000 air traffic controllers, which the FAA has worked to address with plans to hire 1,800 controllers in 2024 and 2,000 this year.
