This post answers the main question about Aviasales and Hotellook API: Why do you need it?          

The API makes it possible to send queries to our server and to receive useful information about flights and hotels. Partners can receive the following data:

• Information about the cheapest tickets to a selected destination;
• Information about airports and airline companies;
• Lists of the most popular flight routes from a selected city;
• Detailed information about a hotel or suite;
• Information about special offers from airline companies and a host of other information.