The cover artwork of the novel Firefox by Craig Thomas depicted a MiG-25, and the plane was described similarly to the MiG-25 in the book.
The Soviet MiG-25 (NATO code-name “Foxbat”) was a high-speed interceptor and reconnaissance aircraft. The aircraft entered service in 1970 and has a top speed of Mach 2.83, powerful radar, and could carry up to four air-to-air missiles.
A capable interceptor, the MiG-25 was widely exported by the Soviet Union.
Subsequent analysis revealed a simple-yet-functional design with vacuum-tube electronics, two massive turbojet engines, and sparing use of advanced materials such as titanium.
The Soviet government put pressure on Japan, demanding the delivery of the purloined ‘Foxbat’ pronto. Since there were no legal reasons not to, the MiG-25 was returned, in dismantled and crated condition. The Japanese did it on purpose to cover up the ‘surgery’ they and the U.S. intelligence experts had undertaken on the MiG.
However the Soviet experts were quick to find out just how much the West actually knew. When the MiG-25 was returned to the USSR it was determined that the Americans had run the engines and measured the aircraft’s infra-red signature and also made a detailed analysis of the systems and avionics, including the radar, and the structural materials. Not knowing how to operate the equipment, the Americans had damaged some of it and had to make hasty repairs (foreign fuses and resistors were discovered in the radar set).
The incident got the world press going wild with stories about the MiG-25 and U.S. Defence Secretary Schlesinger stated that the new Soviet interceptor was a sufficiently potent weapon to bring about drastic changes to the Western weapons systems and strategies.
Belenko’s defection was also mentioned in the novel Firefox by Craig Thomas, on which Clint Eastwood’s movie is based. According to an interesting post appeared on Quora, in the book there’s a mail conversation (the snail mail kind, since it was published in 1977 and takes place a short time after) in which they discuss Belenko’s defection. Someone argues that the new MiG-31 Firefox is not a big deal, since they already have Belenko’s MiG-25, while someone else argues that the MiG-31 is a completely different beast.
Then, as MiG-31 flies for the first time, NATO has everything in the air to spy on it, and nobody could see anything on the radar. They conclude that the MiG-31 not only is faster than anything and features a revolutionary fire control system controlled by thought, but also is invisible to radar, and that they have to steal one.
And that’s when the book begins in earnest, and also where the movie starts.
Since the defection of Victor Belenko was widely mentioned at the time, the publisher had an unusual large first print run, gambling on the publicity of Belenko’s defection to push up the sales.
In fact Craig Thomas was inspired by the awesome performance of the MiG-25, and then Belenko defected as he was finishing the book and thus included in the letters.
Fun fact: the cover artwork depicted a MiG-25, and the plane was described similarly to the MiG-25 in the book. In the sequel, Firefox Down, the description was more like the MiG-31 in the 1982 movie.
Fun fact 2: The artwork on the Swedish paperback translation of Firefox instead depicted a canard and double-delta aircraft, pretty similar to the Swedish JA-37 Viggen.