corporate-wage-slave

You can be rebooked if the flight is cancelled - one rebooking per cancellation, so choose carefully. If the flight operates but now without First, then they may not allow a routing change, but call YouFirst and see what they say to your new routing. Always reseach carefully before flying. However if the flight is some way off, and you have a cancellation that is not resolved, I tend to say proceed slowly - a trip of that sort could have many more changes and you probably have better things to do than micro-manage all of them. With an unresolved cancellation on hand you have more flexibility. If you have already resolved the cancellation, well maybe wait until it happens again.