In this Feb. 18, 2009, file photo, a lineup of U.S. air force KC-135 tanker planes seen at the Manas air base in Bishkek, Kyrgyzstan. The Air Force is poised to reopen the competition between rivals Boeing Co. and Northrop Grumman Corp. for a troubled $35 billion tanker contract. (AP Photo/Azamat Imanaliev, file)
In this Feb. 10, 2009, file photo, a KC-10 plane takes part in a refueling exercise with an Air Force KC-135 plane over the Atlantic Ocean about 300 miles east of New York. After more than 50 years as the military’s gas station in the sky – and a decade of attempts to replace it – the KC-135 is showing its age.