Airlines warn of 5G threat

Airlines are warning that new U.S. C-Band 5G services could potentially interfere with aircraft instruments such as radio altimeters, which display the height between the runway and wheels when landing

Radio altimeter: Signal continuously changes frequency between 4.2-4.4GHz

1. Transmitting antenna

2. Signal bounces back off ground

3. Receiving antenna: Height is measured by comparing frequency of emitted signal to received signal


C-Band: Designated by FCC* as 3.7-4.2GHz

*U.S. Federal Communications Commission

3.7GHz 	3.8 	3.9 	4.0 	4.1 	4.2 	4.3 	4.4

5G networks 3.7GHz to 3.98GHz 		
Guard to stop out-of-band signals 		
Radio altimeters 4.2GHz to 4.4GHz

3.75GHz: Helicopter interference begins

3.95GHz: Commercial aircraft interference begins

Multiple safety systems rely on radio altimeter data


Rate-of-turn indicator

Airspeed (knots and speed trend)

AGL (height above ground level)

Vertical speed (ft/min)

Rad Alt (Radio altimeter)

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Sources: FAA, Radio Technical Commission for Aeronautics
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