I was flying on a FSP mission yesterday in a Learjet. Just before takeoff I noticed that the plane was steering to the right, I just thought I wasnt lined up proprely so I took off anyway.
When I was about to land I took it off autopilot and it veered off to the right. All the guages seemed ok, the engines were going the same speed, the same amount of fuel in both tanks etc etc. I just about managed to land. On the report it said that one of the tanks had developed a major leak. How are you supposed to tell that if the instuments look fine?
You look at the fuel tank indicators. You were most likely looking at the N1, EPR, N2 etc gauges and forgot about the fuel tanks. If you do seem to be producing asymetric thrust, check the engines and then the fuel tanks. It is highly likely it is one of the two 😉