For a new airport shuttle business there are a lot of other financial considerations you need to be concerned about besides depreciation of your vehicles. You need an accountant who will guide you concerning bookkeeping requirements, payroll, taxes, etc. Please consult a local accountant as soon as possible. The accountant will explain your options regarding depreciation.
(Since you have two vans, you must be paying someone else to do some of the driving, so you have employees and a payroll, whether you realize it or not.)
