Several commercial flights repeatedly received mid-air collision warnings near Washington DC last weekend – even though no other aircraft were in the area.
The Federal Aviation Administration (FAA) is investigating reports of false alerts around Ronald Reagan National Airport on Saturday (1 March), one month after a deadly crash near the airport.
Flight crews were issued warnings of other aircraft in their vicinity from the onboard Traffic Collision Avoidance System (TCAS), designed to reduce the risk of mid-air collision, not air traffic control, as they descended to land.
The FAA said in a statement on Monday that TCAS alerts were issued “indicating another aircraft was nearby when no other aircraft were in the area”, reported CNN.
On 29 January, 67 people were killed in a fatal collision between a US Army Black Hawk helicopter and American Eagle flight 5342 over the Potomac River near the Washington airport.
The TCAS system uses radio frequencies to help pilots navigate around each other in the airspace.
According to CBS News, at least 12 flight crews reported false TCAS alerts between 6am and 10am local time.
One air traffic controller was heard telling approaching pilots to “use caution” in the area, reported the outlet.
They said: “It’s been happening all morning. Let me know if you see anything. No one else has seen anything except for on the TCAS.”
“No known traffic between you and the field”, they added.
Three pilots chose to abort landings following the falsely issued alerts and performed a “go-around” manoeuvre.
Robert Sumwalt, former chair of the National Transportation Safety Board, told CBS: "I've never heard of something like this.
"Nuisance alerts, yes, they happen. But not like this where several planes have it at the same location."
The FAA is investigating why the alerts occurred.
Last week, an American Airlines plane discontinued its landing to avoid getting too close to another aircraft departing from the same runway, said the FAA.
American flight 2246 from Boston was arriving at Ronald Reagan airport when it performed a go-around at an air traffic controller’s instruction on 26 February.
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