Flap is marginally significant as the only western ever directed by Britain's Sir Carol Reed. Anthony Quinn is top-billed as Flapping Eagle, a modern-day Native American stuck on a squalid reservation. Though liquored up most of the time, Flapping Eagle undergoes an eleventh-hour social awakening. Making certain that the media is notified, he hijacks a train and heads for Phoenix, demanding full restoration of rights for his people. Played uneasily for laughs, Flap tries to make up for its shortcomings with a 1970s-style tragic ending, but by that time most of the audience has given up. The working title for Flap was Nobody Loves Flapping Eagle, which was closer to the name of source material, Clair Huffaker's novel Nobody Loves a Drunken Indian.
~ Hal Erickson, All Movie Guide