Is it a car? Is it a plane? No, it's both.

The Aerocar is the world's first airplane that can be legally driven on U.S. roads — and it's up for sale on the Internet auction site eBay.

Capable of cruising at 100 mph in the air, this little number can be converted into a car in just five minutes.

Built in 1956 by American inventor Molt Taylor the craft originally carried a modest price tag of $25,000.

But its value has soared — meaning it was listed on eBay today with a Buy It Now price of a far more high-flying $3.5 million.

That's enough to buy several P-51 Mustang fighter jets with enough left over for a Ferrari or two.

Click here to see photos and to read more on this story from The Sun.

Click here to see the eBay sale.