Aptitude tests are a filter, not an end in themselves. You can certainly fail aptitude tests, in which case you could have the best interview and application form in the world, but you still won't get a job! In this case, just passing the tests is unlikely to be enough as there are so many candidates, but Britannia will assess you on all your qualities, not just aptitude. It's quite possible for a candidate with average aptitude, but excellent interview score, to come out ahead of a candidate with an average interview score and excellent aptitude.
Speed is necessary to differentiate between those with 'natural' aptitude, and those who think their way through a test. It has nothing to do with speed being required in a cockpit. Doing things quickly in an aeroplane is a good way to get yourself dead!