The tablets are being tested on two flights departing Los Angles for Tokyo and Shanghai, respectively. The Federal Aviation Administration has approved the iPad tables for all phases of flight, allowing for the first time the use of device during takeoff and landing.
http://www.marketwatch.com/story/american-air-sees-paperless-cockpits-with-ipad-2011-06-16

Also see:
http://www.washingtonpost.com/blogs/dr-gridlock/post/test-moves-airlines-toward-paperless-cockpits/2011/06/20/AGmHM2cH_blog.html

Which mentions another firm, Executive Jet Management, using iPads on-board