On 1 July 2023, a long-awaited deadline finally arrived for airlines operating in the United States. From that day, any aircraft landing in poor visibility had to carry an upgraded radio altimeter — an instrument that measures an aircraft’s height above the ground. The Federal Aviation Administration (FAA) had decided not to delay the rule any further.
Why the deadline mattered
Radio altimeters are essential safety equipment, particularly during landings in fog or heavy cloud, when pilots cannot see the runway clearly. The concern arose because new 5G mobile networks, launched across the country in 2022, use C-band frequencies that sit close to those used by altimeters. Regulators warned that this interference could, in theory, cause an altimeter to display a false reading at a critical moment.
To reduce the risk, the mobile operators AT&T and Verizon had agreed to limit their 5G signals near airports until 1 July 2023. This gave airlines time to fit protective filters or replace older altimeters altogether. As the deadline approached, however, the FAA made clear that it would not be extended, despite requests from parts of the industry.
Were flights disrupted?
By the start of July, more than 85% of the domestic fleet and roughly two-thirds of international aircraft had been retrofitted. Any aircraft that had not been upgraded was prohibited from landing in low-visibility conditions at affected airports, and airlines updated their flight manuals accordingly.
Some carriers were caught short. Delta Air Lines, for example, still had around 190 jets waiting for new altimeters because its supplier could not deliver them quickly enough; most were Airbus models. Even so, the transition passed with minimal disruption, helped by generally good summer weather. By late September the entire US fleet had been equipped, and regulators set a final deadline in early 2024 for the remaining work. The episode showed how closely aviation and modern telecommunications are now connected.
Key vocabulary:
- radio altimeter – an instrument that measures an aircraft’s height above the ground, used especially during landing.
- C-band – a range of radio frequencies used by some 5G mobile networks, close to those used by aircraft altimeters.
- to retrofit – to add new or improved equipment to something that already exists.
- low visibility – conditions, such as fog or heavy rain, in which pilots can see only a short distance.
CEFR Level B2 / ICAO Level 5