Flight Crew Air Transport Pilot (ATP)
Troubleshooting
Aircraft Equipment Problem Less Severe; Deviation - Altitude Excursion From Assigned Altitude; Deviation / Discrepancy - Procedural Clearance
Air Traffic Control Issued New Clearance; Flight Crew Requested ATC Assistance / Clarification; Flight Crew Took Evasive Action
Aircraft; Environment - Non Weather Related
While cruising at FL320; I noticed the 'APPR 2 NOT AVAILABLE' advisory repeatedly showing up on ICAS; followed by the ALT flag on my Primary Flight Display (I was the pilot flying). We were enroute via Q40 in the vicinity of Meridian (MEI). This message called for 'crew awareness ' in accordance with our Quick Reference Handbook. For a few seconds we began to experience altitude variations on the plus and minus sides thus making it impossible to maintain assigned altitude. I asked [the Captain] to request a lower altitude so we could leave RVSM in view of the problem we were experiencing. We were cleared to FL280 and although the advisory would show up once more; the aircraft maintained altitude and no further issues appeared.Shortly after; we heard on the radio another aircraft also requesting altitude change as they could not maintain their assigned altitude either; in the same area we experienced our problem. A few moments later; we heard a [a third] flight asking the Controller if he had knowledge of any problems in that area as they lost their Autopilot and several others systems and were unable to maintain altitude. I think that same flight landed after us and there were firetrucks waiting for its arrival.We discussed the problem during the flight and wondered if this issue was related to a 5G network implementation or something similar. We don't know. I noticed in the area around the fix MISLE; there are several tall antennas; around the area we had this problem. Perhaps look into this 5G network issue more closely and how it possibly affects aircraft at high altitude.
On the Q40 airway between the MISLE nav/fix and BFOLO nav/fix we experienced the 'Approach 2 not available' cyan message on ICAS which indicates crew awareness per the Quick Reference Handbook. Shortly thereafter we experienced attitude; airspeed and auto throttle fluctuations. We notified ATC and requested FL280. We then got permission to leave RVSM. Using the FPA mode and disconnecting the auto throttles we descended to FL280. Although the advisory message appeared once more on the ICAS; everything appeared normal at FL280.Shortly after we heard [another aircraft] report the same issue to ATC. They also had issues maintaining airspeed and altitude and also requested leaving RVSM. We switched Controllers afterwards and then heard [a third aircraft] reporting the same issue except they had more severe fluctuations including the loss of autopilot. Our flight was uneventful at FL280. I reached out to [the third aircraft] to ask of their approximate location and occurrences and it appeared that they had lost their autopilot and some other messages appeared on their screen as well. They were also on the Q40 airway and experienced issues in the same area north of Tuscaloosa Alabama near MEI. [The third aircraft requested special handling] and was number two to land.
Air carrier flight crew reported autoflight anomalies in cruise flight in the vicinity of MEI VORTAC; citing 5G interference as possibly contributing.  Reporter noted that two other air carrier flights in the same area were experiencing similar issues.