Activity in Washington DC’s urban airspace is now being constrained – just a little – by the Federal Aviation Administration following its discovery that the risk of collisions at or near airports across the whole USA is higher than the Agency had appreciated.

This fact emerged during the inquiry by the National Transportation Safety Board (NTSB) and FAA into the 29 January fatal mid-air collision between an army helicopter and regional jet airliner over the Potomac River near Washington Reagan airport.

This decision to reduce traffic, however, is likely to be challenged, and probably quite soon.

The appetite for instantly accessible air transport among DC denizens is insatiable because – they would tell you – of the febrile environment in which many of them conduct their political, lobbying, military or security business in the District. There is always high demand for flights to and from DC’s compact downtown airport close to the heart of the city, and it operates near capacity all the time. Reagan airport is right next to the west bank of the Potomac River, and the other side of the river directly opposite the airfield there is a confluence of urban helicopter routes (see chart below, helicopter routes marked in blue). In addition to that complexity, less than a mile to Reagan’s north west is the Pentagon, with its own heliport.

On the night of the collision the PSA Airlines Bombardier CRJ was approaching Reagan from the south, tracking northward above the Potomac River, intent upon intercepting the instrument landing system (ILS) for runway 01 to land. Meanwhile the army Black Hawk was to the north of Reagan, tracking south along helicopter Route 1 to join Route 4.

Reagan tower asked the CRJ crew if they could accept a late runway change to land on 33, and because the crew could see the lights of both runways they accepted the change, broke off from the runway 01 ILS while still at about 1,700ft, and made a slight right turn to head north to intercept runway 33 ILS. Approaching ILS intercept, the CRJ turned onto final approach at about 500ft. As the CRJ descended through 300ft toward the runway the two aircraft collided.

The circumstances of the collision are not surprising given that these operations were carried out under night visual flight rules (VFR), and the visibility at the time was such that visual identification and separation was practical, if not actually wise. Asked by Reagan tower if they had the CRJ in sight, the Black Hawk crew said they did, although the fact of the collision makes it clear that they had misidentified the regional jet. The lights of the city and airport crowd around on all sides, making misidentification easy.

It has since transpired that the army helicopter was not operating its ADS-B-Out to enable identification by ATC, which it was supposed to do. Right now there is a behind-closed-doors argument going on between the army and the FAA about the military use of ADS-B-Out. The army doesn’t like its aircraft to be trackable, and the FAA insists they must be identifiable in environments like DC airspace. There was, however, no special security classification that demanded stealth for this particular helicopter flight, which was carrying out crew training.

Chair of the NTSB Jennifer Homendy remarked upon the failure of the FAA to respond to the fact that the exact point at which the two aircraft collided had long been identified as a “high risk location”. This failure, she said, was “more than an oversight.” When it was published in early March, the NTSB’s preliminary report on the accident revealed that, between October 2021 and December 2024, there had been more than 15,000 “close proximity events” between helicopters and commercial aircraft near Reagan.

It may be a useful exercise to gather statistics like that to back an argument, but anyone who operates the skies near Reagan knows how busy it has always been, and knows that such a level of traffic density involves considerable risk, especially at night or in poor visibility. The operational requirements for a helicopter heading south on Route 4 are that, when passing Reagan, it is supposed to be at 200ft or lower, so that any aircraft on approach to runway 33 should pass over the helicopter at a height between 300ft and 400ft. The margins for error are tiny, both for vertical separation between the two aircraft, and for obstacle clearance between the low-flying helicopter and ground obstructions, especially risky at night.

The FAA has now decided to close Route 4 whenever runway 33 is in operation. But what if, like the day of the accident, the tower decides at short notice to change a landing from runway 01 to 33? Can sufficient notice be given to helicopter crews using Route 4? The agency plans to allow some limited helicopter traffic on Route 4, but only for “urgent missions, such as lifesaving medical, priority law enforcement or presidential transport”. Unfortunately such flights over this city are common, and there is a question as to who should authorize them. Meanwhile ATC will be expected to prohibit fixed-wing aircraft from simultaneously using Reagan airport’s secondary runways – 15/33 and 04/22. That combination of responsibilities is quite an ask for controllers as busy as those at Reagan.

The FAA’s administrator Chris Rocheleau, at a Congressional Hearing on 27 March, obviously bidding for the Understatement of the Year Oscar, said: “Clearly, something was missed.” The NTSB’s Homendy pointed out that the DC airspace incident data is there to be easily gathered, in the form of voluntary safety reports of near-accidents of all kinds, but admits there is a lot of it. Rocheleau says the Agency is now looking into using artificial intelligence to sort through “tens of millions” of such reports to identify – and flag up – specific risks and trends.

Urban aviation activity like that in Washington DC’s airspace would not be permitted in similar European airspace. Instrument flight rules (IFR) would apply, even if visual separation was used as a backup in VMC. That is not to say Europe is right and America is wrong. Each State has a right to decide what level of risk it finds acceptable, and to determine ways of ensuring that its agreed standards are met, in the knowledge that the authorities will take the rap if they get it wrong.

That is the question Washington DC must answer: how much risk do its denizens want to take, and should they be allowed to take risks at that level? In the 29 January collision all the people on both aircraft died, but the machinery fell harmlessly into the river. In a future collision, that might not be so.

In DC, my money is on a win for the risk-takers who are not prepared to slow down.