An F-16CM fighter jet from the U.S. 510th Fighter Squadron takes off from Kallax Airport outside Lulea, northern Sweden, May 26, 2015, during the Arctic Challenge Exercise (ACE 2015). The United ... more 
An F-16CM fighter jet from the U.S. 510th Fighter Squadron takes off from Kallax Airport outside Lulea, northern Sweden, May 26, 2015, during the Arctic Challenge Exercise (ACE 2015). The United States, Britain, Switzerland, France, Germany, Sweden, Finland, Norway and the Netherlands took part in the military exercise with some 4,000 military personnel and over 100 aircraft. REUTERS/TT News Agency/Susanne Lindholm ATTENTION EDITORS - THIS IMAGE HAS BEEN SUPPLIED BY A THIRD PARTY. FOR EDITORIAL USE ONLY. NOT FOR SALE FOR MARKETING OR ADVERTISING CAMPAIGNS. SWEDEN OUT. NO COMMERCIAL OR EDITORIAL SALES IN SWEDEN. NO COMMERCIAL SALES. less 
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Reuters | Photo By TT NEWS AGENCY / REUTERS
Tue, May 26, 2015 10:05 AM EDT