Massive rollout of mid-band 5G systems might pose an aircraft safety risk by interfering with navigation equipment and causing flight diversions, the US Federal Aviation Administration (FAA) has warned in a series of directives.
The FAA particularly raised concerns about 5G potentially interfering with radio altimeters - sensitive aircraft electronics used by pilots to safely land in poor visibility conditions. Altimeters tell how high an aircraft is above the ground when a pilot cannot see it.
Now, the US aviation watchdog said that planes and helicopters would not be able to use many guided and automatic landing systems at airports with potentially high 5G interference since these systems are likely to be unreliable in these conditions.
Earlier, companies AT&T and Verizon Communications agreed to postpone the commercial launch of their C-band 5G wireless services until January 5 amid the FAA's concerns. Now, the US agency believes that the "unsafe condition" posed by the upcoming use of 5G networks requires immediate action before that date.
"Radio altimeter anomalies" could lead to "loss of continued safe flight and landing" if they remain undetected by pilots or an aircraft's automated systems, the FAA said. Landing during low visibility periods could be "limited" due to 5G concerns, an FAA spokesman told The Verge. One of the FAA directives also said that "these limitations could prevent dispatch of flights to certain locations with low visibility, and could also result in flight diversions."
The agency also said that its two directives issued on Tuesday, which also include revised safety guidelines, were particularly aimed at gathering "more information to avoid potential effects on aviation safety equipment."
The agency still believes that "expansion of 5G and aviation will safely co-exist." It is also in talks with the Federal Communications Commission (FCC), the White House, and industry representatives to work out the details of limitations that are to be outlined in the coming weeks.
The FCC said it looks forward to "updated guidance from the FAA." The aviation watchdog said that specific notices could be issued for areas "where the data from a radio altimeter may be unreliable" due to 5G signals.
AT&T and Verizon said in late November they would take precautionary measures to limit the potential interference of their networks for at least six months. The FAA argued on Monday that was insufficient.
Verizon responded on Tuesday by saying that there was "no evidence" of C-band 5G networks actually posing any risks to aircraft in "dozens of countries" that already use them. The company added it plans to "reach 100 million Americans with this network in the first quarter of 2022."