Is it a bike? Is it a plane? Three Czech companies have teamed up to make a prototype of an electric bicycle that successfully took off today inside an exhibition hall in Prague and landed safely after a remote-controlled, five-minute flight. Looking like a heavy mountain bike, it weighs 209 pounds, with two battery-power propellers in the front, two in the back, and one each on the sides. An official with Duchek, a maker of bicycle frames, says more powerful batteries will be needed before a human takes a two-wheeled flight. (A dummy rode in the saddle this time around.) No word yet on when it might be available to consumers.