After four years of flight tests, the first upgraded Lockheed Martin C-5M Super Galaxy was redelivered to the U.S. Air Force late last month. The most significant of the more than 70 changes in the reliability enhancement and re-engining program is the replacement of the four GE TF39 turbofans with modern GE CF6-80C2 engines that deliver 22 percent more thrust, improved fuel consumption and lower noise. A total of 52 C-5s will be modified, almost all C-5Bs built in the 1980s. The Air Force has not yet decided whether to re-engine a similar number of older C-5As.