had initially been designated Rescues 1 to 5. His inspiration for the launch sequences of Thunderbirds 1, 2 and 3 originated from contemporary US Air Force launch procedure: Anderson had learnt how the Strategic Air Command would keep its pilots on permanent standby, seated in the cockpits of their aircraft and ready for take-off at a moment's notice. In the DVD documentary The Thunderbirds Companion, Anderson explained how a rise in filming costs had made overseas distribution revenue even more important and essentially caused Thunderbirds to be made "as an American show". During the character development and voice casting process, the Andersons' main priority was to ensure that the series had transatlantic appeal, thus increasing the chances of winning an American network deal and the higher audience figures that this market had to offer. Filming Thunderbirds was filmed at APF's studios on the Slough Trading Estate between 1964 and 1966. In preparation, the number of full-time crew was expanded to 100. Shooting began in September 1964 after five months of pre-production. Due to the new series' technical complexity, this was a period longer than for any of the earlier productions. To speed up the filming, episodes were shot in pairs on separate stages and by separate crews (designated "A" and "B"). By 1964, APF was the UK's largest commercial user of colour film, consuming more than three million feet (570 miles or 910 kilometres) of stock per year. As with APF's previous three series, the Andersons devised Thunderbirds as a 25-minute show. In late 1964, Alan Pattillo, a longtime writer and director for APF, was made the company's first official script editor. This move was aimed to reduce the burden on Gerry Anderson who, while reserving his producer's right to overall creative control, had grown weary of revising scripts himself. Direction of episodes was assigned in pairs: veterans Pattillo and David Elliott alternated with the less-experienced Desmond Saunders and newcomer David Lane for each month's filming. Due to the difficulties of setting up takes, progress was slow: even on a productive day, it was rare for the crew to complete more than two minutes of puppet footage. In a contemporary interview, Hill noted that Thunderbirds contained several times as many shots as a typical live-action series. He explained that rapid editing was necessary on account of the characters' lack of facial expression, which made it difficult to sustain the viewer's