I’m a 5 million miler with American. I have lifetime Executive Platinum status. Yes, this status carries across all One World carries. You don’t get every benefit, but most. All my trips to Bangkok from the US are on Japan, Cathay, or Qatar. All 3 of these recognize my status. In irregular ops situations I go to the head of the line. I get to use all the First Class lounges. And on occasion get operational upgrades. Because my status is lifetime, I don’t need to fly One World to retain it, but it serves me well.