Since every other reviewer here has commented on the relation between 'Zero Hour!' and its latter-day spoof 'Airplane!', let me be the first to contribute a review of 'Zero Hour!' on its own terms.
First, 'Zero Hour!' was obviously shot on a low budget. It uses a lot of stock footage - much of which is badly varied, mismatched as, for example, the airliner in the film is a four-engined DC-4 which, in the film's cuts to stock footage not only appears as a DC-4 in three different airline paint/livery schemes, but it's also represented in still other stock shots by footage of a twin-engined DC-3 and a twin-engined Convair. At the crash landing ending the model used is of a four-engined airliner which is not a DC-4 (it looks like a post-WWII British airliner whose maker/name/identification escapes me at present). Another key to the low budget is the film's inexpensive (I'm trying to be charitable) sets; and at one point a close-up of the plane's instruments are not airplane instruments at all, but a cheaply mocked-up row of three generic panel lamps above which is hand-painted LEFT-NOSE-RIGHT to represent the cockpit's landing gear lock-down indicators. One of the aerial shots of the DC-4, which appears in the film as the aircraft is on final approach, also presents a gaffe: in this stock shot the airliner's Number 4 engine's propeller is feathered - stopped! - which is absurd because in the plot the DC-4 suffers no engine failures.
Worse, though, than 'Zero Hour!'s' jumble of airliner stock footage are the obvious models used for the film's introductory combat sequence. The credits open over fine stock footage of early WWII Spitfire Mk I's in formation. But this footage gives way to models-on-wires "bathtub" shots, and I believe most, if not all, of these shots of model Spitfires and Messerschmitts were simply lifted from an earlier film (which may have been 1956's 'Reach For The Sky'). Worse still, some of the close-ups of what are supposed to be the Canadian squadron's Spitfires actually show actors (who are unrecognizable in their face-covering goggles and oxygen masks) seated in the cockpits of full-size Messerschmitt models! In one egregiously inaccurate (and thus confusion-making) small-model shot a Messerschmitt in Nazi insignia actually represents the crash of a Canadian Spitfire. But this sequence gets even worse than that: at one point it cuts to a model shot - of static-suspended models wobbled by off-screen fans - of a radial-engined Curtiss Hawk 75 painted in French Air Force camouflage and insignia (which, we are supposed to believe, is one of the in-line engined Canadian Spitfires!) "pursuing" a Messerschmitt model! The acting here is not bad - some of it is actually quite good, especially from the splendid, but chronically under-appreciated and underrated, Dana Andrews. It's the cheesy Arthur Hailey dialogue that's the real culprit that robs 'Zero Hour!' of enduring appeal (and which, I'd argue, together with the unintentionally comical plane-switching stock footage, most inspired the later spoof movie); but the cheesy dialogue's not helped, at a few points, by rapid, hectic, less than first-class editing that also betrays the low-budget on which 'Zero Hour' was produced.
The score isn't great, yet it's actually rather good - especially for a suspense film of its time. Some of the makeup is overdone - especially the excessive perspiration on the faces of the ill and the panicking aircrew and passengers and on the anxious ground controllers, which was apparently applied with a surfeit of zeal. Women's hairstyles here are reserved, but expertly done; and the costuming is quite good for a low-budget effort. Also, one of the airline office men begins the film, before he's been through any of the suspenseful trials that ensue, already wearing much more than a five o'clock shadow of whiskers: in 1957 this was most definitely not a tonsorial custom, especially for airline/technical employees - in those days a man's boss could and would call him on the carpet for having had the bad manners to have come to work so direly unshaven.
Former pro football star Elroy "Crazylegs" Hirsch is a trifle stiff as the captain of the airliner; but then a lot of athletes-turned-actors of that day were also rather wooden in their acting (Chuck Connors comes foremost to mind, especially in his earliest, bit parts). The rest of the supporting cast is comprised chiefly of Canadian talent who do a solid job (notwithstanding that they too labored under the often cheesy lines they were given to read) of moving the story forward and fleshing it out as well as can be expected in a low-budget film.
On its own terms, then, on the IMDb house scale of ten, I believe I have to give 'Zero Hour' 6 stars.
First, 'Zero Hour!' was obviously shot on a low budget. It uses a lot of stock footage - much of which is badly varied, mismatched as, for example, the airliner in the film is a four-engined DC-4 which, in the film's cuts to stock footage not only appears as a DC-4 in three different airline paint/livery schemes, but it's also represented in still other stock shots by footage of a twin-engined DC-3 and a twin-engined Convair. At the crash landing ending the model used is of a four-engined airliner which is not a DC-4 (it looks like a post-WWII British airliner whose maker/name/identification escapes me at present). Another key to the low budget is the film's inexpensive (I'm trying to be charitable) sets; and at one point a close-up of the plane's instruments are not airplane instruments at all, but a cheaply mocked-up row of three generic panel lamps above which is hand-painted LEFT-NOSE-RIGHT to represent the cockpit's landing gear lock-down indicators. One of the aerial shots of the DC-4, which appears in the film as the aircraft is on final approach, also presents a gaffe: in this stock shot the airliner's Number 4 engine's propeller is feathered - stopped! - which is absurd because in the plot the DC-4 suffers no engine failures.
Worse, though, than 'Zero Hour!'s' jumble of airliner stock footage are the obvious models used for the film's introductory combat sequence. The credits open over fine stock footage of early WWII Spitfire Mk I's in formation. But this footage gives way to models-on-wires "bathtub" shots, and I believe most, if not all, of these shots of model Spitfires and Messerschmitts were simply lifted from an earlier film (which may have been 1956's 'Reach For The Sky'). Worse still, some of the close-ups of what are supposed to be the Canadian squadron's Spitfires actually show actors (who are unrecognizable in their face-covering goggles and oxygen masks) seated in the cockpits of full-size Messerschmitt models! In one egregiously inaccurate (and thus confusion-making) small-model shot a Messerschmitt in Nazi insignia actually represents the crash of a Canadian Spitfire. But this sequence gets even worse than that: at one point it cuts to a model shot - of static-suspended models wobbled by off-screen fans - of a radial-engined Curtiss Hawk 75 painted in French Air Force camouflage and insignia (which, we are supposed to believe, is one of the in-line engined Canadian Spitfires!) "pursuing" a Messerschmitt model! The acting here is not bad - some of it is actually quite good, especially from the splendid, but chronically under-appreciated and underrated, Dana Andrews. It's the cheesy Arthur Hailey dialogue that's the real culprit that robs 'Zero Hour!' of enduring appeal (and which, I'd argue, together with the unintentionally comical plane-switching stock footage, most inspired the later spoof movie); but the cheesy dialogue's not helped, at a few points, by rapid, hectic, less than first-class editing that also betrays the low-budget on which 'Zero Hour' was produced.
The score isn't great, yet it's actually rather good - especially for a suspense film of its time. Some of the makeup is overdone - especially the excessive perspiration on the faces of the ill and the panicking aircrew and passengers and on the anxious ground controllers, which was apparently applied with a surfeit of zeal. Women's hairstyles here are reserved, but expertly done; and the costuming is quite good for a low-budget effort. Also, one of the airline office men begins the film, before he's been through any of the suspenseful trials that ensue, already wearing much more than a five o'clock shadow of whiskers: in 1957 this was most definitely not a tonsorial custom, especially for airline/technical employees - in those days a man's boss could and would call him on the carpet for having had the bad manners to have come to work so direly unshaven.
Former pro football star Elroy "Crazylegs" Hirsch is a trifle stiff as the captain of the airliner; but then a lot of athletes-turned-actors of that day were also rather wooden in their acting (Chuck Connors comes foremost to mind, especially in his earliest, bit parts). The rest of the supporting cast is comprised chiefly of Canadian talent who do a solid job (notwithstanding that they too labored under the often cheesy lines they were given to read) of moving the story forward and fleshing it out as well as can be expected in a low-budget film.
On its own terms, then, on the IMDb house scale of ten, I believe I have to give 'Zero Hour' 6 stars.