At the time, for a U.K. cinema release to be classed as a main feature, it had to be at least 75 minutes long. On the last day of filming, with only 30 minutes of studio time left, the crew realized that they only had enough footage and script to stretch to 72 minutes. This would have meant that this movie could only be used as a supporting feature, which would have meant a financial disaster for the backers. Frankie Howerd spotted a phone box prop and, with the clock counting down, improvised on the spot a three-minute scene of him calling his old grandmother. With no time for a run-through, the entire sequence was used unedited in the final movie.
Speaking on BBC Radio 4's "Loose Ends" in September 2016, Petula Clark (Lee Nicholls) recalled this as a "dreadful film", noting that the noxious artificial fog used in the studio to disguise the conspicuous lack of background scenery made the cast fall ill.
Miss Beeston (Margaret Rutherford) wonders why the wartime "FIDO" fog removal system could not be used at the airport. She is referring to to the "Fog Investigation and Dispersal Operation" system used at sixteen RAF airfields during WWII. It consisted of pipes laid parallel on either side of a runway through which fuel was pumped and set alight. The heat from the flames would evaporate fog directly over the runway. It was tremendously expensive, using 125,000 U.S. gallons (400,000 liters) of fuel per hour. The last time it was used was in 1952, due to advancements in radar and other radio navigation and landing aids for aircraft.