American and British Airways have been marketing allies for decades, co-participating in each other's mileage programs and co-anchoring the oneworld global airline alliance.
They have also been die-hard competitors, in particular on trans-Atlantic routes where the two carriers have battled each other fiercely for passengers flying between the U.S. and London.
Because of their combined dominance across the Atlantic, American and British Airways were prohibited from joint marketing trans-Atlantic flights in their longstanding frequent flyer program tie-up.
In other words, a member of American's AAdvantage program could earn and redeem miles for flights throughout British Airways' extensive network, but not on its routes between the U.S. and the U.K.—exactly the routes the average AAdvantage member would be most interested in. (Flights from and to Canada and Mexico were not covered by the exclusion, giving AAdvantage members a way, albeit an inconvenient one, to circumvent the restriction.)
Similarly, members of British Airways' Executive Club program could earn and redeem miles on all American flights, except for those between the U.S. and the U.K.
For years, the policy has been a source of confusion and frustration to members of both airlines' programs.
Beginning today, October 1, AAdvantage members can earn and redeem miles for all British Airways flights, including the previously excluded trans-Atlantic flights. And Executive Club members can do the same for all American flights.
The change follows American's and British Airways' receipt of antitrust exemption from U.S. and European regulators, which was also extended to Finnair, Iberia, and Royal Jordanian.
Also effective today, AAdvantage members will earn full credit for some discounted coach fares (K, L, M, N, O, G, Q, S, V booking codes) that previously earned just 25 percent of the miles actually flown.
And lastly, AAdvantage Executive Platinum and Platinum members will earn elite status bonus miles. There's no elite bonus for Gold members, however. According to American's FAQ: "Since their frequent flyer program only features two elite levels, this benefit will not apply to the third elite level in the AAdvantage program, namely AAdvantage Gold."
That's the good news, but it's not the whole story.
While the availability of British Airways award flights to and from London is an ostensive positive for AAdvantage members, the value of that new benefit is significantly undermined by British Airways' particularly onerous fuel surcharges, which will now apply to award tickets issued on all British Airways flights. For trans-Atlantic flights, those surcharges range between $107 and $141 each way in coach, depending on flight distance, and between $157 and $205 each way in first class.
All told, this is a mixed bag. Earning miles for British Airways flights to London is a significant new benefit for AAdvantage members. Redeeming miles for British Airways' flights? Not so much.
Still, it's a net positive for a solid program.
This article originally appeared on FrequentFlier.com.