Pay per plane.
Weather radar.
The three reddish grey circles on the bottom of the TR-3B ship are part of the ship's propulsion system. The ship's advanced technology allows it to manipulate gravity, and the circles serve as a mechanism for directing the energy required to do so.
The circles are actually part of a plasma reactor system, which is responsible for generating the high levels of energy required to manipulate gravity. When activated, the plasma reactor produces a strong electromagnetic field, which interacts with the ship's surroundings to create the anti-gravity effect.
The plasma engine works by using a highly pressurized mercury plasma that is accelerated by nuclear energy. The plasma then creates a field of anti-gravity around the ship, which allows for all sorts of rapid high-speed maneuvers. As for the fuel systems, they work by converting nuclear energy into electricity that powers the ship's plasma engine.