How long does it take an aircraft to become available to be sold once removed from a route?
Routes typically are scheduled 2 days in advance (Can lead to flights scheduled over 2 days in advance) so if you remove a plane from a route, but do not cancel all active flights it will keep flying the already scheduled flights so around 48-72 hours before it is all done and can be sold.
It’s instant if you’ve already cancelled the route.
So it will be 2 days as I want to swap out an aircraft, or can you cancel the route, then add in the other aircraft and save route and wait for tjhe route schedule job to pick it up tomorrow?
Yes you can do that. Cancel the route(aircraft will finish flying the leg it’s currently on and just become idle after it’s turn time), swap the aircraft with your second one, and then once you activate the route again the new aircraft will be scheduled to fly the route.
What you can also do and what I usually do is turn off the route then copy it and put the new aircraft on the copy. That way the aircraft I want to replace can finish making it’s money and I can go ahead and schedule the new one at the same time. Although if your airline is larger, then cancelling the route may just be a drop in the bucket as far as profit loss.