we flew Heathrow/Chicago/Memphis and believe me changing planes in Chicago was a nightmare, we had to take our luggage from the carousel at Chicago and then go through immigration & customs [ took ages we only got our 2 hr later connection by the skin of our teeth] and then re check in our luggage again, but no body told us we then had to change terminals--well we had to catch a small monorail to get to the Memphis departures, the whole thing was a nightmare, moral is dont change in Chicago if theres an alternative.