A radar altimeter is a piece of avionics tech that tells pilots their altitude to a very high degree of accuracy without needing to be calibrated with the ambient barometric pressure. It only engages at low altitudes, like 2500 feet and below and so it's only used on approach. It's important because there are instrument approaches you can perform in low visibility that require you to reach certain thresholds of speed and altitude at various waypoints and they require a radar altimeter. Without it, you'd have planes going around more often in fog and rain because they can't meet the requirements of the approach plate.

It has nothing to do with 5G conspiracies. It's real interference on a sensitive and important instrument.

The aircraft manufacturers need to work on shielding the radar altimeters from interference but until then, I think this is a reasonable request.