Long before this model gained popularity with astronauts - Jack Swigert wore it on the troubled Apollo XIII mission - it soared to fame with commercial pilots.
As a matter of fact, Rolex originally created the GMT Master in 1955 to allow Pan Am pilots on transatlantic flights to simultaneously monitor both GMT and local time.
Pan Am is no longer flying (much to my relief), but the GMT Master is still ticking along half a century later, with a redesigned look sporting a new winding crown, and a new security clasp with a rapid extension link on the Oyster bracelet. One of the models also has a two-colour dial to differentiate day from night.(e.g.Rolex Replica GMT-Silver)
Just set the 24-hour hand and the 12-hour hand to the same hour while in your local time zone, then re-adjust the hour hand and the date either ahead as you travel east, or back as you travel west. The movement in the GMT Master II is unique because it allows you to adjust the hour and the date backwards just as easily as forwards.
