[3]A joint British-American plot is devised to steal a highly advanced Soviet fighter aircraft (MiG-31, NATO code name "Firefox") which is capable of Mach 6 (hypersonic flight), is invisible to radar, and carries weapons controlled by thought.

Evading the Soviets' attempts to stop him, Gant barely reaches the Arctic ice pack and lands, making a rendezvous with a U.S. submarine whose crew refuels and rearms the aircraft.

However, Gant's last-minute refusal to kill Voskov has consequences; the Soviet pilot flies the second prototype, with orders to intercept him at the North Cape area.

[6] Filming occurred in 1981 at a number of locations including Vienna, Austria; Montana; California; London and Greenland's Thule Air Force Base.

[9] Special effects supervisor John Dykstra pioneered a new technique for shooting the complex flying sequences, called reverse blue-screen photography.

This enabled the shiny black model to be photographed flying against a clear blue sky and gleaming white snow; compare this with traditional bluescreen technique used in The Empire Strikes Back.

[10][11] Author Howard Hughes gave Firefox a negative review, "Watch the trailer, read the book, play the game — just avoid the film, it's another Eiger Sanction.

"[12] Vincent Canby's review in The New York Times made a similar assessment, zeroing in on Eastwood's lack of control over the plot line.

"[15] Gene Siskel of the Chicago Tribune gave the film two-and-a-half stars out of four and wrote that it was "generally entertaining," but "would be a lot more so if Eastwood, who served as producer-director, had excised some of the laborious buildup to the final shootout.

"[17] Gary Arnold of The Washington Post wrote, "Both loyal fans and neutral observers may agree that Eastwood has steered himself into a peculiarly murky flight path on this occasion," calling the plot "far-fetched" and expressing disappointment that "the Firefox doesn't look all that formidable on the screen ...

The only in-flight special effect that stirs the imagination is the parallel curtains of water that suddenly erupt in the wake of the plane as it whooshes across the ocean.