The main reason flight search is so far behind the rest of the tech world is that the inventory is so difficult to access. You have to either be very well connected and able to persuade one of the gatekeepers to give you access on a trial basis, or have money to purchase data from commercial suppliers like ITA, OAG, ATPCO, each of which is hugely costly and limited in the type of data they provide and the completeness of coverage.

For bootstrapping a travel search product, you're best to get busy building crawlers to scrape airline websites directly.