ADS-R and TIS-B NOTAMS?

A noticeable increase in ADS-R (ADS-B Rebroadcast) and TIS-B (Traffic Information Service-Broadcast) NOTAMs has drawn attention across pilot communities, with operators and flight crews reporting these advisories appearing with unusual frequency across the National Airspace System. Both services are FAA-operated ground-based uplink functions that are integral to the ADS-B In traffic picture displayed in aircraft cockpits. ADS-R bridges the two ADS-B frequencies — 978 MHz UAT and 1090 MHz ES — by having ground stations rebroadcast traffic transmitting on one frequency to aircraft equipped to receive the other, ensuring cross-frequency traffic visibility. TIS-B, meanwhile, provides radar-derived traffic data on non-ADS-B-equipped aircraft to ADS-B In users, filling in targets that would otherwise be invisible to the cockpit display.

When these services go offline or degrade, the FAA is required to issue NOTAMs alerting pilots that the ground station uplink is unavailable in a given area. A surge in such NOTAMs typically points to one of several causes: scheduled maintenance on specific ground stations, unscheduled outages due to equipment failures, network-level infrastructure work, or broader systemic issues affecting the FAA's ADS-B ground network. The ADS-B ground infrastructure was largely deployed between 2013 and 2020 as part of the NextGen program and portions of that network are now aging into their first major maintenance cycles. FAA budget pressures and technical workforce challenges in recent years have also affected the pace at which ground station issues are resolved, potentially contributing to a backlog of outages that generates a high volume of active NOTAMs simultaneously.

The operational implications for working pilots are significant and frequently underappreciated. An ADS-R or TIS-B outage does not affect ADS-B Out performance — aircraft continue to broadcast their own position normally — but it directly degrades the traffic picture received by ADS-B In displays and EFB applications. In an area with an active ADS-R outage, a UAT-equipped aircraft will not see 1090 ES traffic through its cockpit display, and vice versa. In an area with a TIS-B outage, non-ADS-B-equipped aircraft tracked only by radar will disappear from traffic displays entirely. This creates a condition where a pilot's situational awareness tool appears fully functional while silently presenting an incomplete traffic picture — a potentially dangerous scenario in busy terminal environments or high-traffic VFR corridors.

Part 91 and Part 135 operators should build NOTAMs for ADS-R and TIS-B service outages into their preflight planning workflows the same way they address NAVAID or approach procedure NOTAMs. These advisories are frequently buried in bulk NOTAM feeds and can be easy to miss, particularly when using automated briefing tools that may not flag them with adequate prominence. Crews relying on ForeFlight, Garmin Pilot, or panel-mounted traffic systems should understand that those displays are downstream of the ADS-B ground network — any degradation in the ground infrastructure translates directly into a degraded traffic picture, regardless of what the display appears to show.

The broader trend here reflects ongoing tension between the FAA's mandate to operate a robust NextGen surveillance infrastructure and the resource constraints affecting that mission. The ADS-B mandate became a requirement for most controlled airspace in January 2020, and the aviation community broadly accepted the transition with the expectation that the supporting ground network would be reliably maintained. A period of elevated outage NOTAMs challenges that assumption and underscores a fundamental limitation of ADS-B In as a traffic tool: it is not a certified separation service and was never designed to replace see-and-avoid or ATC traffic advisories. Pilots who have grown accustomed to high-fidelity traffic pictures on tablets and glass panels need to treat ADS-R and TIS-B NOTAMs as meaningful operational data, not administrative noise.