It is important to note that 5G and aircraft radar altimeters do NOT operate or coexist on the same frequencies. The problem is that 5G frequencies are close t

It is important to note that 5G and aircraft radar altimeters do NOT operate or coexist on the same frequencies. The problem is that 5G frequencies are close to radar altimeter c-band frequencies and the issue lies with certain aircraft that do not have sufficient band pass filters in place on their radar altimeter receivers, so when a strong 5G signal is present the aircraft's radar altimeter can be overloaded with adjacent channel interference. Retrofitting band pass filters on existing aircraft radar altimeters isn't a trivial task - avionics changes to aircraft are a multi-year project since extensive testing is done on anything electrical installed on an aicraft. Additionally, some 5G infrastructure equipment may need additional band pass filters installed to prevent spurious transmissions outside of their assigned frequency ranges in areas near airports. If you aren't familiar with a bandpass filter, it basically filters all RF outside of a certain frequency range. Sensitive receivers can naturally be overwhelmed by RF outside of the receiver's frequency range, and preventing that RF getting to the receiver in the first place is the role of a band pass filter.