Brazil's Azul has started selling airfares to 35 destinations served by United Airlines through an interline agreement, taking the first step in a partnership that the two airlines first announced in June.

By mid-August, Azul will sell airfares to the over 350 cities served by United, says Azul.

With United inventory now available through Azul, passengers will be able to travel on both airlines on a single ticket and check their baggage through to their final destination in Brazil or the USA.

United announced an investment of $100 million in Azul in June in exchange for a 5% stake. The two airlines eventually plan to be close codeshare partners, which has to be approved by regulatory authorities.

The two carriers have also started offering each others' frequent fliers reciprocal benefits.

Azul and United became interline partners in 2014, but that deal was only one-way, and involved United selling Azul's fares. The 35 United destinations that Azul is selling tickets for now include United's hubs at Chicago O'Hare, Newark Liberty, and Washington Dulles as well as international destinations such as Lisbon, Madrid, Frankfurt, London, Hong Kong, Paris and others.

The two carriers together serve more than 450 destinations.

Source: Cirium Dashboard