The United Kingdom CAA in October 2002 conducted a series of laboratory tests which exposed general aviation avionic equipment to simulated cellphone transmissions. A VHF radio, a VOR/ILS receiver with HSI and secondary indicators, and a remote gyro compass system were used. At high signal levels, similar to that attainable from a cellphone 30 cm from the equipment or its wiring, anomalies were produced on all equipment readings except the glide slope indication. These tests confirmed onboard cellphones as an interference source, and endorsed current legislation restricting their use on aircraft.
The bolding is mine: cell phones
can cause an issue in the cockpit. I've never seen any confirmation of issues from a distance, let alone the 9th row.
Unfortunately, I don't have the UK CAA report. That reference is from this 2011 NZ accident report:
Piper PA 31-350 Navajo Chieftain ZK-NCA, controlled flight into terrain, near Christchurch Aerodrome, 6 June 2003*
Aviation Reports -
Aviation Reports
Although I still think it likely that the crash was nothing to do with anomalies and everything to do with the fact that the pilot was using the phone on approach.
* No points for guessing why I'm looking at this crash
