I would say Concord but proffesional I am not.

I like the SR-71 Blackbird. +6

The Concord. But they don't make them any more. However the research that went into the building of Concords produced so much of additional knowledge and understanding of the aero-spcace physics, I understand.

I agreed - only I use term SST. Miss the fast trip across Atl.

I would say the Supermarine Spitfire for its role during world war two, especially the Battle of Britain.

The Vulcan Bomber. A perfect combination of form and function, and a noise to strike fear into the heart of God!

Cessna 172

The Douglas DC-3 Dakota has to be the most significant plane ever made! They were first built in the 1930’s & are still flying today! Great plane & very versatile too!! :-/

OK here is my answer in my opinion http://en.wikipedia.org/wiki/DC-3 The Douglas DC-3 is an American fixed-wing, propeller-driven aircraft whose speed and range revolutionized air transport in the 1930s and 1940s. Because of its lasting impact on the airline industry and World War II, it is generally regarded as one of the most significant transport aircraft ever made.

The B-29 as it was lend leased to Soviet Union in WWII and it was the basis of everything that followed in the Soviet Union and the US for planes with pressurized cabins

Civil Transport: DC-3 Military Transport: C-47 (a green DC-3 with "no-class" seating) Close Air Support: P-47 and A-10 (Thunderbolt I & II) Reconnasiance: U-2 Daragon Lady Attack: A-20, B-25G Fighter: P-51D (over the C), F-15 Strategic Bomber: B-52, B-2 Light Bomber: B-25C (Not the D... I live in L.A.) General Aviation: Cesna 337 Super Skymaster

In the sense of greatest meaning largest,: http://en.wikipedia.org/wiki/Spruce_Goose The Hughes H-4 Hercules (registration NX37602) was a prototype heavy transport aircraft designed and built by the Hughes Aircraft company. The aircraft made its only flight on 2 November 1947. Built from wood due to wartime raw material restrictions on the use of aluminum, it was nicknamed the "Spruce Goose" by its critics. The Hercules is the largest flying boat ever built, and has the largest wingspan and height of any aircraft in history. It survives in good condition at the Evergreen Aviation Museum in McMinnville, Oregon, USA.

CF-105 Arrow http://en.wikipedia.org/wiki/CF-105_Arrow

Ultimate: Boeing 747. Too stuborn to know that it can't lift 850,000 lbs. But it did it. Military Transport: C130. Like the DC3, strap a jeep under the wing and it will get it there. Close Air Support: A-10 Warthog. Let's build a gun and then let's put some wings on it. Reconnasiance: SR71 Oh, SAM coming... let's just open the throttle a little more. Attack: Agaqin, A10 Warthog, nothing more to say. Fighter: Prop: P51, Drop the tanks and still two hours of loiter time over Japan. Jet: F14 Tomcat, Kills like an F15 but turns like an F16. Strategic Bomber: B17. Sure, small bomb load but the tail and wings can be shot to hell and it will still bring it's crew home. Light Bomber: Baltimore Whore. If the pilot knows how to use the throttle and the rudder all the rest is cake. Utillity: Cessna 180/185 Official state bird of Alaska. Kick it, hit it with a hammer and it will get pissed off and get you into or out-of a strip where it does not fit. Trainer: Cesna 150/152 Too underpowered and too stupid to know they can't fly. Stress (spin them) to 6gs and they will still bring you home to a 40kt touchdown and make you look good doing it in a 30kt crosswind !!!

The C-130 Hercules gets my vote. One of the most widely used and versatile airplanes world-wide. It's been in production for over 50 years. http://en.wikipedia.org/wiki/C-130_Hercules

Do you mean greatest, or biggest. What about that thing with lots of engines built by Howard Hughes. It flew once, not very high but, it did fly. The B2 Bombers that had wheels at the ends of the wings to stop them dragging on the tarmac. The spy planes, made up from carbon that could fly so high and weren't spotable by radar. Take your pick, I would like to hear what is or was the greatest?