I had a conversation with a buddy a while back, that is very senior at a major. He told me the 737-800's take some getting used to with the landings. If I recall correctly he was making some adjustments like bringing them in a little hot on purpose. Apparently they cracked the airframe prior to cracking the code... Also, I notice they have a ton of new airframes on order. Judging from their history and recent developments that is apparently foresight to account for loss of airframes rather than due to expansion plans.