Says Jack Hunter in House of Horror: The Complete Hammer Films Story: "Initially planned for a 1972 release as another entry into the prehistoric series begun with One Million Years B.C. This would have added a Lost World element, pitting WWI German airmen against the winged beasties, as seen in Creatures the World Forgot, though Hammer lost their taste for expensive special effects quite early on, despite making more money on their first dinosaur flick than on any other production."
There's an alternate universe somewhere in which this won the 1972 Best Film Oscar and BAFTA, thanks largely to Peter O'Toole's stirring turn as Capt. Jack Sommerisle opposite Klaus Kinski's "Red Baron" von Richthofen, who meets a grisly end indeed.
Also of note is Maggie Smith as Lady Roxton, who is secretly the mother of Felicity Kendall's adventurer-aviatrix Beatrice Fairwind. With Kurt Russell as the plucky sidekick "Sparks," Maximilian Schell as Dr. Favreau, and introducing Madeline Kahn as "Kitty" Caprice.
Scenarist Francis Ford Coppola, building on his work scripting Patton, gained high acclaim for his vividly drawn and dimensional characters and thematically layered action sequences. Director John Boorman still lost out to William Friedkin for The French Connection, but you know it was all just political.
Now that I think about it, the SciFi (or SyFy or Sigh-Fie) Channel could dust off these old Hammer notions and make them now. Gotta be better than, say, Sharktopus.
Music: Nina Simone, "Sinner Man"
Near at hand: Starbucks London city mug