I know this is an older topic but I think it should be made known that you CAN get Aetna to cover Similac Alimentum!
They will try and tell you no but do not be fooled! We had to call 3 times to find out just why they were saying no to it.. As it turns out it is not for the fact that they just won't at all.. They list it as a "Food supplement" and not a babies main food! You have to tell them that your child has a medical need for it and has doctors orders to use it.
They will ask you to have you childs doctor call a number to tell them that it is indeed the babies only food intake and that they need it..
Then they will cover the costs!

I know just how hard it is to pay for it when you have a child that can only eat it. I hope that this info helps others make ends meet like it helped our family!