When I was in Riyadh I remember seeing a company that would airship your Lambo or Ferrari to the south of France so that when you took a trip to Europe to avoid the desert heat in July/August you could still rip around in your sports car violating every law imaginable.

For the OPs sister in law I'm sure land transport is the way to go. That is how everyone else, e.g. the military when you move cross-country, does it.