Kate Upton recently had some fun on a photoshoot for the Sports Illustrated Swimsuit Issue. The sexy 21-year-old has been the cover girl for the past two years. This time around she'll be on the back cover. Kate stripped down for a sexy shoot on a zero G plane for the issue's 50th anniversary.

Check out this behind the scenes video below.  

The Sports Illustrated Swimsuit Issue is on sale now! 

Photos: 50 Years of SI Swimsuit Covers

Photo: swimsuit.si.com