The MiG-31 (МиГ-31 in Cyrillic script), NATO reporting name "Firefox", is a fictional aircraft appearing in Craig Thomas' novels Firefox and Firefox Down, as well as the Clint Eastwood film based on the former (and the laserdisc arcade game based on the film).
The Firefox is an interceptor aircraft with stealth capabilities, to the point that it is invisible to radar. It is powered by two incredibly powerful "Turmansky" turbo-ramjet engines that permit flight at hypersonic speeds, but their exhaust gives the Firefox a prominent infrared signature.
The Firefox's most famous feature is its Thought-Controlled Weapons System, which uses signals from the pilot's brain to target enemies and fire weapons; however, it only responds to commands thought in Russian. The Firefox's weapons consist of up to four AA-6 Acrid air-to-air missiles (modified for thought guidance), two 23 mm cannons, and four Rear Defense Pods on the wings, which fire explosive charges at a pursuing aircraft or missile.
Other capabilities of the Firefox include a 3,000-mile (4,800 km) range and a flight ceiling over 120,000 feet (37,000 m). To give the pilot full situational awareness the aircraft also includes a camera system that allows the pilot to see images ahead of, below, and directly behind the aircraft on his console. Mitchell Gant uses this system several times during his flight to keep track of missiles, and other aircraft pursuing him.
Two production prototypes were built before it was to be deployed into active service for the Soviet Air Force. The first prototype was stolen by Mitchell Gant operating on behalf of the Western intelligence community. The second prototype intercepted Gant and the two aircraft entered into combat with Gant destroying his adversary.
The Firefox's appearance differs between the first novel and film. The version in the novel resembles a MiG-25 "Foxbat", much like the real Mikoyan MiG-31 "Foxhound".
Source: Wikipedia, "Fictional military aircraft", available under the CC-BY-SA License.