Definitely 747 and Concorde, as far as commercial airliners go. The 737, while ubiquitous, is not particularly distinctive. And the A380, while unique, is not yet widely recognizable. I had a friend who travels quite a bit look at it and say, "What is that thing?"

As for military aircraft, you have to go with the Lockheed SR-71A Blackbird. I think most would still recognize the F-14 Tomcat. Anyone who has been to an airshow would probably recognize the F/A-18 Hornet (Blue Angels) and F-16 Fighting Falcon (Thurnderbirds). The A-10 Warthog is certainly distinctive. The F-15 Eagle is probably the most well-known fighter plane of the last generation. Anyone familiar with the Vietnam era will certainly recognize the F-4 Phantom, and anyone who has taken an American history class should recognize the B-52 Stratofortress. And I think there is also a place for the F-117 Nighthawk on this list.