For most experimental aircraft, earning an airworthiness certificate is enough of a challenge. But the Terrafugia Transition is a unique type of flying machine, requiring approval not only from the FAA, but also from the USDOT's National Highway Traffic Safety Administration (NHTSA), since this air / land hybrid is likely to spend just as much time cruising down the highway as it will flying 5,000 feet above. The Transition is now slightly closer to takeoff, with the NHTSA granting exemptions for absent airbags, a missing electronic stability system, and the plane's lightweight polycarbonate windows (polycarbonate is lighter than automotive safety glass, and won't shatter and obscure a pilot's vision in the event of a bird strike). Unfortunately the Transition still has other hurdles to fly over -- its cabin is limited to carrying 330 pounds when fully fueled, including passengers, and the price has jumped 41 percent, to $250,000. In the meantime, Terrafugia hopes to move forward with production later this year, bringing the 'flying car' slightly closer to a runway (and highway) near you.