WASHINGTON D.C. (WSJ) — Air-safety regulators recently stepped up scrutiny of midair-collision warnings around the U.S., prompted by an increase of close calls at a handful of busy airports, according to people familiar with the matter and industry documents.

Neither the Federal Aviation Administration nor airlines think there are imminent risks to passengers, and they haven’t issued emergency orders or mandated other changes to carrier operations. Rather, safety experts said they are concerned that potential collision risks could rise as traffic continues to rebound from the Covid-19 pandemic.

Airborne close calls requiring airline pilots to take last-second evasive maneuvers have been largely eliminated by advances in technology over the years. Since last summer, however, some FAA and airline officials have become concerned that instances of commercial aircraft flying dangerously close to other planes rose in 2021 from pre-pandemic 2019 levels near some airports, according to the documents and officials familiar with them.
Senior regulators, veteran airline managers and pilot-union leaders held a series of discussions and conducted fresh studies of the issue during the summer through late last year, documents summarizing some of those meetings show. The documents identified escalating midair risks in 2021 near Minneapolis-Saint Paul International Airport and Hollywood Burbank Airport in Southern California. The documents, which haven’t been reported before, designated additional “airports of interest” requiring further analysis. They include New York’s John F. Kennedy International Airport, Miami International Airport, and Honolulu’s Daniel K. Inouye International Airport.

Earlier this year, a different industry document identified the Dallas region as among those showing a pattern of increases in midair-collision warnings. Flight safety is the purview of the FAA, and airport operators haven’t participated in the FAA-industry groups evaluating airborne risks. Representatives from those airports either had no comment or noted the FAA’s regulatory role.

Denver International Airport, according to the documents and separate FAA safety updates, is of particular concern to government and industry officials. For more than a decade, safety officials have tried to reduce potential collision risks that are most acute during landing approaches to some runways. The FAA, which for years has worked on safety enhancements at Denver, recently launched another safety review there, an FAA spokesman said.

A spokeswoman for the airport said officials at Denver are monitoring progress toward a potential solution.

Some senior flight-safety officials said the increases in midair-collision warnings may be explained in part by pilots, air-traffic controllers, and other aviation professionals grappling with the widespread shutdown inactivity in 2020 as the pandemic ensued, followed by the intense recovery.

The FAA, working with officials from various aviation groups, told airlines last summer to consider monitoring several issues related to airborne-collision warnings. Joint FAA-industry groups have stepped up efforts to analyze and counter the trend, according to industry documents and officials involved. The spokesman for the FAA said data the agency collects through voluntary reporting programs has been effective in identifying midair-collision threats and other risks.

Meanwhile, data collected by the National Transportation Safety Board through a mandatory reporting system show increases in airborne-collision warnings near several major hubs. The NTSB’s data, which tracks incidents differently than the FAA, indicates collision warnings rose around several busy airports last year compared with pre-pandemic traffic in 2019. At Newark Liberty International Airport in New Jersey, for example, reports of such incidents rose to 11 from three during that period. They also increased to four from one at Los Angeles International Airport, and to 15 from 11 at Fort Lauderdale-Hollywood International Airport in Florida, according to the NTSB data, which includes passenger airliners, large cargo aircraft, and other commercial operators. Representatives for Newark, Los Angeles, and Fort Lauderdale had no comment.

The number of warnings captured by the NTSB is minuscule compared with the roughly 6.2 million domestic airliner flights last year tracked by the federal Bureau of Transportation Statistics, but they represent some of the most serious potential risks in aviation. Each incident tracked by the NTSB involved what the board’s reporting criteria categorized as requiring pilot action in response to “a substantial risk of collision.”
The last midair crash in the U.S. involving a major passenger plane occurred about 36 years ago, before advances in cockpit technology, above Cerritos, Calif., and resulted in the deaths of more than 80 people. Domestic passenger airlines haven’t suffered any kind of fatal crash in 13 years.

The full significance of the NTSB data and industry documents viewed by The Wall Street Journal isn’t clear. The data from the NTSB isn’t reliable enough to make definitive risk assessments around specific airports because airlines are inconsistent in reporting close calls leading to collision-avoidance warnings, a spokesman said.

The safety board, which investigates transportation accidents but has no regulatory authority, reviews each report it receives to track potential safety issues and seeks to determine the seriousness of the events, the NTSB spokesman said.

In recent months, joint FAA and industry safety teams have reviewed some of the same airports where the NTSB data shows warnings increased, according to people familiar with the matter.

At the heart of the safety reviews by regulators are Traffic Alert and Collision Avoidance Systems, on-board airliners, and other types of planes, that alert pilots to potential midair hazards. The equipment has drastically reduced midair collisions over the decades. Known as TCAS, the systems initially provide pilots with automated warnings about nearby air traffic.

If planes continue to converge, TCAS becomes an aviator’s ultimate lifeline by issuing more urgent, automated voice commands to descend or climb—technically called resolution advisories—that pilots typically are obliged to follow. Those advisories are tracked by both the NTSB and FAA.

Cockpit crews are expected to react in a few seconds and at most, typically have about half a minute to take emergency action to prevent an airborne catastrophe. Denver International, which has described itself as the third-busiest U.S. airport, illustrates the difficult technical challenges of combating midair risks. The airport’s mile-high elevation and layout can confuse TCAS software, resulting in more-frequent warnings requiring pilots to go around for another landing attempt, according to government, industry, and independent safety experts.

Many airlines and the FAA describe those warnings as “nuisance alerts.”

To avoid longer flights and increase runway capacity, many pilots approaching certain Denver strips are allowed to turn off the TCAS collision-avoidance feature. That is permitted under strict conditions, such as when planes approach runways in daylight and with enhanced monitoring by air-traffic controllers, according to pilots and flight-safety officials.