I need a webapp built

I'm after a website/webapp to be built so that I can utilise empty legs of aircraft charter flights. Operators (air charter companys) have a secure account. they add basic info, departure point, arrival point, flight time, max payload, aircraft type, price, date and time. The system must take this and add it to a page of available flights (think like when you book a flight with an airline). When it adds the flight to the system, it must also add a little markup of a fixed percentage (this must be able to be individually customised by site admins.) Customers have no need for an account, they select a flight and add details (passenger numbers, names, weights, and notes) then pay for the flight. After this happens, the site generates a purchase order and forwards it to the operator who books it into their booking system. Must be able to easily refund customers if the flight doesn't go ahead.