THIS IS NOT LEGAL ADVICE BUT GENERALLY...
As has been asked already - what is the governing law of this contract ? Jurisdiction ?
In England and Wales a court will generally only enforce a provision like this if it is reasonable.
This is all to do with what is known as restraint of trade - basically a person is entitled to undertake a lawful trade when and where he wants.
Any provision such as the one you mention is, prima facie, unenforceable. The provision will only be enforced if it is reasonable.
To my mind this MIGHT mean "you cannot fly type X for [2 airlines that are my biggest competitors] for 2 months after leaving", not you can never fly type X for any airline.
The former seems more reasonable than the latter.
* AS I SAID BEFORE THIS IS NOT LEGAL ADVICE