Two tier travel affiliate programs
A two tier affiliate program is a program where you earn money from affiliate links and banners on your own website + you can earn a percentage from other affiliates you refer.
There are not many two tier travel affiliate programs, but one of them is Travel Payouts.
By using the Travel Payouts affiliate program you can earn money both on selling hotels and flights. It works like a search engine you can integrate on your website or blog, or you can use text links.
You'll also earn a commission on the sales made by other affiliates you refer to the program.