I've not yet ever flown between Mexico and the US. However, I've crossed between the two countries many times via Baja land borders. Unless something
has changed, you keep your FMM when exiting Mexico, and if it is a 180-day FMM, it can be used to re-enter Mexico, as long as your re-entry is within
the period of validity for the FMM. I have done this many times at the San Ysidro-Tijuana crossing. Obviously, if there is not much time left on your
FMM, it would be better to get a new FMM upon returning to Mexico. But, if you still have considerable time left on the FMM, it could save you the
expense of getting a new one. |