Norway was 5th country with an Open Skies agreement with USA from 24 April 1995. In other words Norway was way earlier in the green than most EU countries that got part of Open Skies 30 April 2007 (over 12 years after the three Scandinavian countries). Norway and Iceland became party to the U.S.-EU agreement pursuant to an agreement signed and provisionally applied June 11, 2011.
Source:
http://m.state.gov/md114805.htm