Most dSLR's come with a kitlens, but the range isn't big enough to do aviation photography. It's usually in the 18 - 55 - 70 mm range. These lenses aren't the best either. Although Olympus gets very good reviews for it's kitlenses.
I'd advise that you go to a shop, look around and try-out some camera's. You must understand that you choose a system. Most dSLR users invest in better lenses over time and the lenses outlive the camerabody. So you'll have to stick to lenses for you brand. ( ex. you can't put Canon lenses on a Nikon)
Basically you should look for the best camera ( MP's, abilities, functions, etc.) for your budget.
Entry camera's are:
Canon 350D and 400D ( rebel XT and Rebel XTi in the US)
Nikon D40 and D40x ( but these are meant for 'normal' users, if you intend to go further in photography, you'll want a better cam like the D80 + they don't have an onboard focusmotor, so you'll have to buy lenses with this engine and you might guess that these are more expensive)
Pentax K100D Super
Olympus E410 and E510
Sony Alpha 100
Some only have 6 or 8 MP instead of the nowadays usual 10 MP, but that isn't a problem until you want to make large prints of your photo's.
Check
www.dpreview.com for more reviews.
Also check out prices for lenses and accesoires, because one brand is more expensive than the other.
Basically, there aren't any bad camera's out there. You have to choose what you like.
As far as lenses go, usually 300 or 400 mm zooms are used for aviation photography. You can find cheap zoomlenses and more expensive ones. Once again, you should read reviews to decide what lense will meet your expectations and budget.
www.photozone.dewww.fredmiranda.comEnjoy your search!
Omag