1. Boeing B-52 This plane will see at least 80 years of service before it's gone completely. By FAR the best combat aircraft ever built.
2. Boeing 707 This plane led the way for comercial jet aviation, not to mention the various military versions that are still in service, AWACS, JSTARS, KC-135. This plane will also see at least 80 years of service if not more.
3. Boeing 747 The Grand Daddy of the super jumbos. Over 40 years in service and this airframe is STILL in production.
4. Douglas DC-3 Rock solid design that has withstood war and peace time missions. After over 70 years of flying, they are still out there doing what they were designed to do.
5. Lockheed SR-71 This plane set so many records it's not even funny. On it's last official flight it set a new world speed record. The technological achievments alone brought about by this plane earn it a place in the top 5 greatest.