The interference I experienced was just a couple years ago, from an LTE handset. It had fallen back to 2G mode due to the weak signal at altitude. As I underst

The interference I experienced was just a couple years ago, from an LTE handset. It had fallen back to 2G mode due to the weak signal at altitude. As I understand it (and someone more versed in cellular backends can correct me), the reason why 2G GSM interference was so noticeable was because the TDMA-based radio would switch on and off at an frequency within the audible range, and once inductively coupled with a nearby audio cable would be strong enough to play sound through speakers. That doesn't mean newer cellular radios don't interfere. They can, just not audibly. Newer CDMA-style radio modes (used on LTE/5G) aren't switching on and off like the TDMA ones did, but they're still emitting the same amount of power. In particular, I'd be most worried about the aircraft's navigation radio. The technology used for ILS/VOR navigation is technologically simple, and easy to interfere with. A car driving past the wrong area of the airport can disrupt the signal. (There's "ILS Critical Areas" on airport taxiways that are marked off for this very reason, and ground controllers will prevent aircraft or vehicles from entering those areas when there's an aircraft on an ILS approach.)