Goofs

The Hudson bombers taxiing out in Canada do not have the mid-upper turret installed. When the German fighter is attacking them, they all have the turrets installed.

When the bombers are being ferried to England, MacLean spots the enemy aircraft high on the port side and flying against the group. A following shot shows the Messerschmidt on the starboard side and flying in the same direction as the group.

When the Hudson bombers are taxiing out for takeoff, the same planes are shown several times. Tis can be seen by the plane closest to the camera: it is number 2951 and is repeated 3 or 4 times.

When "Alabama's" plane is shown on its way to the bomb range, there are no bombs hanging from the wings in the long shots of the actual aircraft.

An RCAF flying instructor (James Cagney) takes off in plane number 2689 but doing things his way instead of by the book crashes and is court martialed. At the court hearing it's stated he crashed plane 6228J.

The film plays a recording of Churchill's famous 'We shall fight on the beaches' speech as the characters listen to it. But while Churchill did make the speech to the House of Commons in June of 1940, it was not broadcast at the time. The text appeared in newspapers and excerpts were read on the radio by a BBC announcer. The speech heard in the movie was 're-enacted' by Churchill nine years after that date. So the characters would not have been able to hear Churchill give the speech himself.

The flag observed flying at the "backwoods" settlement and displayed on the walls inside the pub is the British Union Jack. The proper flag would have been Canada's flag which, until 1965, was a red flag with the British Union Jack in the upper left corner and the full color crest of the Canadian Dominion in the lower 1/3 of the right side.

Considering that the bombers were gutted to lessen weight and add fuel tanks to maximize their range and endurance, flying from Canada would have had them arrive at England's west coast. In fact, they are shown flying over water. But they are attacked by a Messerschmitt Bf-109, which did not have the range to reach the west coast, let alone make several passes and then return to its base, even if it had drop tanks, and would not in any case risk time and fuel patrolling that area.

When Johnny is watching the troops march past the Parliament Buildings on Wellington Street, he turns and sees the front of the War Memorial, which is only visible from Elgin Street to the south.

As MacLean is coasting up to the dock, he's moving at would be at least speed walking pace; he throws his mooring rope to Emily on the dock. After she catches it, the view switches back to him and his plane, and it has completely stopped. There is no way a float plane could stop that quickly.

(at around 30 mins) After the sea plane has taken off, the blurry image of an insect can be seen walking across the lens right to left as Tiny and Emily walk on the dock.

(at around 48 mins) When Brian looks out the window and sees Johnny walking, the closeup shot of Dennis Morgan walking is obviously a set with a background screen.

(at around 46 mins) When Brian and Johnny are fighting, it's clear that none of the three punches make contact (especially the last one).

After MacLean is done showing off to Johnny Dutton, he tells MacLean to again execute a slow turn to the right. However, the plane is then shown turning to the left.