Big Kahuna Burger - as you're obviously a CPA, we don't need to tell you about stuff such as the UCC or ASA, do we?
411A is quite correct (as usual). You can't just take an arbitrary term to use for depreciation - it's set out in the standard accounting code. A new aircraft can be depreciated over 15 - 20 years (depending on type; in general smaller aircraft have shorter depreciation terms); and in the case of older aircraft such as the L1011s we can depreciate the book acquisition cost over an agreed term (usually 3-5 years or the working life if less) plus any additional work carried out on the aircraft over its working life (ie a an annual C check counts as an operating expense as it lasts a year; whereas a D check would be depreciated over the five years or so it lasts for).
Don't forget, either, that the depreciation allowances are only really effective if you have profits to write them off against. This is why it's very rare for startups to buy new aircraft (jetBlue is about the only one I can think of except for EVA Air - and they used the Evergreen tax base). On the other hand, most of the big lessors are owned by major financial services companies such as ILFC (owned by AIG) and GECAS (owned by GE) which have huge amounts of cash surpluses and profits they need to offset.
Airbourne - when the time is right - we've got recessions/economic downturns on at the moment, which are bad news for any startups...
Innuendo / Celtic Emerald - I didn't start this thread ... I'm just responding to it. And at 3 posts a day, each taking around 5 minutes to do, I'm still left with 23h 45m per day. More than ample to do what I have to do!