I booked a trip on AA.com and it asked for my information such as middle name birthdate and gender. When I saw my ticketed ticket it only showed my first and last name. On the AA Website it says that it does not matter whetehr my middle name was present or not to get FF miles. My thinking is that the TSA system is internal and they get the name on the list. When you checkin online possibly the Secure Info goes to the TSA or when the plane takes off. Just my intuition.