I have purchased tickets from travel on other airlines using only my first and last name (LASTNAME/FIRSTNAME MR) with no problems. Also, this is how my travel agent enters my name into my computer.

When calling United to check on a fare, I was put on hold by the agent and heard something about United requiring my full legal name (LASTNAME/FIRSTNAME MIDDLENAME MR).

Since I am planning to get a CX/UA RTW, and my AAdvantage(to get miles on the CX portion) and Mileage Plus accounts are only registered as "FIRSTNAME LASTNAME", will buying my ticket as "LASTNAME/FIRSTNAME MIDDLENAME MR" have any effect on me getting my miles correctly credited to my account?