Call of Duty: Modern Warfare three has a total of 50 achievements/trophies to complete however you will find that there is one secret achievement you can unlock, although you are not given any information on this task it is actually called "Flight Attendant"

To find out what you have to do to complete this, click on this link

Read more: http://gameolosophy.com/games/mw3-secret-achievement/#ixzz1jzRvWNks