In 2002, I heard about the PLT challenge after discovering this board. I had just completed a lot of flying and actually got AA to do a retoractive challenge starting about two months prior from the date that I asked for the challenge. It was a "one-time exception".

It probably helped that I had a lot of future travel on the books with them as well, so much so that the future travel added to what I had already done was greater than 50K miles/points.

It took a few e-mails and I actually had to help the agent I talked to with the math, but I also got retroactive 100% flight bonuses as well, so it is possible even if the flights have already posted.