Say you own a 20-year-old car and intend to drive it beyond the year 2050. It will need some fixing. A challenge similar to that continually faces Whiteman Air Force Base, home to the B-2 stealth bomber. Many aircraft parts made in the 1980s, when the first of 21 B-2s rolled out of a Northrop Grumman Corp. hangar, are as obsolete today as the floppy disk. Yet the plan is to keep those bat-winged bombers flying, and eluding the latest in radar technology, until 2058. The Pentagon is moving forward with a $2 billion, 10-year effort to modernize the fleet’s...