Japan Airlines and British Airways are taking a major step towards their proposed joint business venture by beginning code-share flights on the Tokyo-London route.

The two carriers have been tightening their relationship since the Japanese government granted them antitrust immunity in May. This allowed them to discuss fares and schedules, and they will now be aligning their fares on the Tokyo-London flights.

While important, this step is still short of the revenue-sharing joint venture that the two carriers intend to set up. The airlines “continue to work towards” that goal, but no exact date has been set for it, a JAL spokeswoman tells AviationWeek. JAL already has a revenue-sharing partnership in place with American Airlines on Japan-U.S. routes.

Between them, JAL and BA have 19 flights a week between Tokyo and London. They each have a daily service between Tokyo Narita and London Heathrow, and in addition BA flies five times a week between Tokyo Haneda and Heathrow.

Under the code-share arrangement, which begins Oct. 1, the carriers will be able to market each other’s flights. So travelers will be able to book a return itinerary combining JAL and BA flights.

The two airlines were already code-sharing on 23 routes beyond London to Europe, and on eight domestic and international routes beyond Tokyo.