Supposing your situation is as you say, i.e. (JOHN/SMITHMR rather than SMITH/JOHNMR), it should be ok as long as the letters in the word matches your ID.

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http://www.flyertalk.com/forum/delta...et-ok-fly.html
http://www.flyertalk.com/forum/bmi-d...d-i-worry.html
http://www.flyertalk.com/forum/trave...ng-usa-eu.html