I am guessing that its not a cell phone. We ran tests at our field and found that a cell phone needs to be within 10 feet to affect a plane. Farther away and there is no interference. With the cell phone close to the plane, some of the servos would jump and jitter intermittently. Immediatly noticeable if you have the engine running and the throttle servo starts to twitch! Thats how I first found out about the problem. I was breaking in a new flyers engine and the plane was held back by a rope so it didn't go anywhere. The engine started to rev up and down when a guy walked up with his cell phone on. Back to your problem, I have seen about 5 planes at our field now that suddenly do a turn to a slight angle and stay there until they crash. Being curious about what happened I stuck around until the plane was retreived and inspected. In all the cases the cause was the battery pack for the receiver was depleted. Since the elevators suddenly went down and stayed there, it sounds a lot like the same symptoms. You said you had about 75 flights on the plane and now you have a technical problem so maybe time to do a cycle on the reciever pack and see if thats got something to do with it?? If nothing else its a good start. [8D]