Having experienced this (hence the name FallenAngel), the answer is or was "it depends." Granted my experience was almost 35 years ago, but things still appear to be relatively the same. I was attrited from advanced jet. I was not given the alternative of switching to helicopters. For Marines, prop pipeline as a separate line to winging was just starting. I was made an Infantry Officer and still say it is one of the best things that ever happened to me. (As an aside, it still bothers me to have gotten so close to my wings but not received them. I do, however, still cherish my carrier qualification certificate from landing on the Lady Lex in T-2s). I know at least one Marine who was given a shot at helos, although his problems occurred in basic jets. Now that I think of it I do not know any Marines that were switched to helos from advanced jet. Of course, there are not many of us that made it that far, only to get attrited in advanced jet. Usually, it occurs much earlier. I knew several naval officers who were switched to prop pipeline from both basic and advanced jet. As far as when you learn your air frame, it was not until shortly (one or two weeks) before receiving your wings. While not impossible, it would be unlikely that you would get this far and get attrited. Good luck.