In different countries, 5G is rolled out in different spectrums, power levels, and directions.
The new 5G network in the US is operating at 3.7 – 3.98 GHz, the Airplanes Radio Altimeter uses 4.2 – 4.4GHz. This leaves only 220 MHz of separation and creates concerns that this could interfere with the aircraft radio altimeter.
In Europe, the 5G is using the range of 3.4 -3.8 GHz which leaves more separation to the Radio Altimeter compared to the US operation.
On December 17, 2021 EASA | European Union Aviation Safety Agency Safety Information Bulletin (SIBNo. 2021-16) stated