As sigma says, this is really only doable when your airline is brand new and you have a very small fleet, but even then, you're probably better off just giving all yoru planes constant routes and not worrying about switching them around for C-Checks.
Though, sometimes early in the game I'll do a similar thing when I'm fighting the incumbant carrier in town - I'll move a route to a newly arrived plane so it has no gaps, and after the C-check finishes that plane gets a new set of routes. That helps keep the staff costs down for the planes in maint and the RI building. Once the fleet gets to about 30 planes, this really isn't doable and by that point if you're making so little that a c-check hurts, you've got bigger issues than that...
This idea is good for real .. ex. many airlines always have a spare a/c for a delay or maintainance check each day to prevent a possible delay that might happen.
may be we can add it in the next version of game.
There's been a rather vivid thread in the features section talking about the concept of airplane pooling, and having enough aircraft in the pool to cover maint and the schedule as a method for accounting for this.