chocsaway08: BA do accept equivalent qualifications to those listed, but one HNC on its own would not be enough. It's quite complicated, but one HNC is worth roughly as many UCAS points as an A at Advanced Higher, which is 130. That's the equivalent of 2 Bs at Higher.
However, when you've passed your degree you should exceed the minimum entry requirements, and in any case your best bet would be to finish your degree off anyway in my opinion.
tennisten: There needs to be some method of differentiating applicants without having to employ someone to look at each one individually (it would take too long and cost too much money). On average, those with better A-Levels will outperform those with poorer A-Levels. Clearly this might miss some talented individuals, but those individuals can still go and get better A-Levels if they want to.
But it's not just about doing extremely well in the COMPASS tests. If that's all there was to it then selection wouldn't require academic qualifications. The acedamic requirements are there to demonstrate that you can work on a range of subjects at the same time and work hard for an extended period - because training to become a pilot is about working hard as well as having the aptitude. In other words, they could take on the most intelligent people in the country (who would probably perform extremely well in the COMPASS tests), but they might all fail the course because they can't handle the workload. This - incidentally - is also the reason why the range of A-Levels is not so important, although Maths and Physics will clearly be advantageous.
FlyVeryHigh: What's wrong with English, Psychology and Religion as subjects? They might not be as relevant to the mechanical workings of an aircraft, but there is so much more to being a pilot than that. BA are looking for well-rounded individuals who value different cultures and religions; so religion as a subject can really enhance your application. And a knowledge of psychology is also very helpful and relevant; and indeed if you look at many AAIB or NTSB accident reports you'll see how psychology can (and does) often play a factor in human error.