It’s worth remembering that the film's creation was geared toward achieving commercial success in America, which explains the liberties taken with the narrative about an RAF squadron sent to demolish a German facility for rocket fuel hidden within a Norwegian mountain range. George Chakiris, following his role in "West Side Story," and Cliff Robertson head up what is admittedly a rather stiff, but competently produced, wartime story. While the aerial sequences are visually acceptable, they don’t particularly impress considering the year—1964—and the characters feel somewhat predictable, making it difficult to take them very seriously. The supporting actors perform adequately, though ultimately, apart from Ron Goodwin's noteworthy soundtrack, this feels like an underwhelming project.

Source on TMDB