Try any good bookshop or Amazon and ask for mental aptitude books. As Spanner says you won't (probably) find anything airline specific but books like "How to win at Aptitude tests", Iain Maitland, at least get you in the right frame of mind with worked examples and loads of practice material. So when you're asked a long multiplication question you won't waste time racking your brains wishing you'd paid more attention in GCSE maths, or if you have to make a square out of 5 different pieces you'll have some method.
If you have an interview try and find out the type of test they use, that way you can do an internet search on it. Although you won't know or find the exact same questions at least you may be able to find the format. Every little piece of info to give you a heads up will help.