For $4 million plus overages (paid out over four years), investors can buy their own Model J — a 169-foot-long (51 meters) aircraft that can carry up to 10 people (eight passengers and two pilots), or about 2,000 lbs. (907 kilograms) through the air, thanks to its helium-filled blimp-like body, gas-electric hybrid engines and rotational wings with propellers.

But don't call it a plimp outright. That word is trademarked and meant to be used as an adjective, said James Egan, a Seattle-based attorney who is the CEO of Egan Airships, maker of the plimp-hybrid aircraft. [In Images: Vertical-Flight Military Planes Take Off]

The idea came to Egan in childhood, as he was playing with helium balloons and balsa-wood gliders. He noticed that these wooden gliders had a slower descent when he tied helium balloons to the planes' wings and tails