I put this in the NYC forum but since it deals with AA's terminal 9 in JFK, maybe it should be asked here?

We will be arriving in JFK on a Thursday morning in Aug next year from GRU at 6am. One US, one Australian passport. How long do you think it would take to clear immigration & customs? How much time would we save if we don't have checked bags? I have been known to wear three pairs of jeans just to get my carry on small enough to carry on, then put the other two back in the backpack after we get on the plane!

So if anyone has done this route, what is best case scenario and worst case for getting through?