I gave up on sea-top ferries when I discovered Silver City, a mid-century phenomenon that flew cars over the Channel. The people sat in the 15 lap-belted seats that ran in a few rows athwart the plane — a Bristol Freighter, I think. Wide things. I’m not sure how many cars fit, but there was usually even last-minute room for a Mini. It fit neatly crosswise in the nose.
I remember a car carrying flight to Rotterdam when I was taking Mama to Moscow in a Mini (alliteration gets to me). I sat in one of those seats, gazing at my red, black-topped Mini some 20 feet away. The ultimate carry-on.