US lawmakers are getting closer to requiring that aircraft flying in US airspace be equipped with Automatic Dependent Surveillance-Broadcast In (ADS-B In) systems.
The US House of Representatives is poised vote on a revised version of a bill called the ALERT Act that would require aircraft to have the technology. The vote is planned for the evening of 14 April.
Though the measure is expected to pass with bipartisan support, it remains controversial, with the Air Line Pilots Association in opposition.
The planned vote is the latest step in a months-long legislative response to the deadly January 2025 midair collision near Ronald Reagan Washington National airport.
The Senate and House introduced competing bills to address the need for better collision-avoidance systems. But lawmakers and lobbyists have sparred over them – specifically over ADS-B In requirements. That technology, which builds on the ADS-B Out systems aircraft are already required to carry, gives pilots more information about nearby aircraft.
House lawmakers recently tweaked their bill — the Airspace Location and Enhanced Risk Transparency (ALERT) Act — to include ADS-B In requirements because the prior version was criticised for failing to explicitly mandate the technology. For that reason, the National Transportation Safety Board (NTSB) did not support the prior version.
But the latest version would require aircraft have two systems: ADS-B In and Airborne Collision Avoidance System X (ACAS X). Those technologies would need to be integrated, meaning ADS-B In data would feed into ACAS X, helping improve that system’s traffic alerting function.
ACAS X is the newest iteration of the Traffic Alert and Collision Avoidance System (TCAS) already required for large jets. The systems warn pilots of nearby aircraft and issue “resolution advisories” that instruct pilots to climb or descend to avoid collision.
The bill would require airlines, charter aircraft and other types to have the technologies by end-2031. Rotorcraft and powered-lift aircraft — the category under which electric air taxi developers are seeking certification — will also need the systems, though the bill does not set a deadline for those types.
The NTSB has given its approval, saying the bill’s requirements “would address its recommendations”. The agency has since 2008 urged the Federal Aviation Administration to require ADS-B In.
The bill is therefore likely to pass the full house vote on 14 April, says a source with the House Committee on Transportation and Infrastructure.
It will then head to the Senate for consideration. That body has been seeking to pass related legislation called the Rotorcraft Operations Transparency and Oversight Reform (ROTOR) Act, which has always specifically required ADS-B In — and not with ACAS X. Due to differences between the bills, Senate and House lawmakers will likely need to negotiate a final legislation.
But opposition to the ALERT Act remains, with ALPA saying, “The measure does not implement the strongest
possible pro-safety measures, and we do not endorse the bill”.
The union says ACAS Xa — the variant for large commercial aircraft — is not yet commercialised and that standards do not exist for integrating ACAS Xa with ADS-B In. It also notes that ACAS X “is suppressed” at altitudes beneath 1,000ft, “when pilots need situation awareness the most”. The FAA does not yet mandate ACAS X.
DATA PROTECTION REQUIREMENT
The House bill would prohibit ADS-B data from being used for “the purpose of obtaining revenue” from aircraft operators.
That provision addresses concerns from general aviation groups. The Aircraft Owners and Pilots Association, for instance, has complained that the FAA has used ADS-B data to wrongly pursue enforcement action against aircraft operators, and that airports can use the data to levy fees.
ADS-B In received little congressional attention until after a US Army helicopter collided with a PSA Airlines CRJ700 regional jet on 29 January 2025 near Reagan National airport, killing all 67 people aboard both aircraft.
The NTSB attributed the collision to numerous factors, including the FAA’s failure to require ADS-B In. Other factors included air traffic control shortcomings due partly to high workloads and to heavy air traffic, failure by pilots to visually maintain separation and failure by the US Army to ensure pilots were aware of altimeter errors.
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