Originally Posted by
BriGuy
Although many FF programs allow you to get flight credit in their own programs for flights flown before joining their FF program, most FF program Ts&Cs I have seen do not allow you to obtain partner credit retroactive to your joining their program. (I admittedly have not checked the FF program Ts&Cs for the airlines you listed.)
Actually, it's even easier then to get a credit in their own program. Partners don't know when you became a member of a partner program when you request from them to post missing miles from flights. You just need all the documentation to be in order. I did it for myself and my family.