What would be the maximum travel range do you believe that can extracted from a motor glider?

If you have a motor glider that had a motor that recharged off solar or had an alternator that recharged the battery to run it, would it be possible to fly across the US West coast to East coast with some help of the jet stream maybe? If you could not find or catch any terms and got too low, you can just fire up the engine and climb to where you can glide again. Providing you can stay awake because travel would be terribly slow, what would stop you from making it?