The U.S. Air Force is still upgrading the KC-135 aerial refueling tanker despite having a replacement in development now.
The Stratotankers’ F-108 engines will be getting new components under the C-PUP program, that will improve fuel burn and increase reliability.
[thumb]http://www.airforcetimes.com/news/2012/08/airforce-kc-135-upgrades-planned-082412/[/thumb]