If I need to fly, I transport my Paddy Cafferky harp in a custom-built hard case built by Ray Doherty . I have fit this case into the following vehicles:
In all of the above cars, I put the back seats down, and voilà! There’s space for the harp case, my luggage (sometimes more luggage, depending on the vehicle) plus driver and 1 passenger. If you’re transporting me and my harp case, here are the dimensions.