When asked, most aviation enthusiasts will name aircraft such as the Spitfire, B-17, Lancaster, Mustang, the Me-109 or Zero — all undeniably great aircraft and all which earned their spurs in combat. Perhaps one of the most important factors in earning the title of Great Aircraft is timing - that is being around when the opportunity to prove greatness arises. All the previously mentioned aircraft served during World War Two and fought in some of the most significant air battles of the 20th century.

The Avro Lancaster: One of the top contenders in our search for the Greatest Combat Aircraft of all time

There's many aircraft that have been on the cutting edge of technology and were the best of their type at the time, however unless circumstances allowed these aircraft to demonstrate their capability, this alone doesn't seem to be enough to bestow greatness on the design. Examples of these might include such types as the Hawker Hunter. Regarded by many as the most graceful fighter jet ever flown, the Hunter is from the same design team as the WW2 Hurricane led by Sidney Camm. From an era when the F-86 and MiG-15 were regarded as the ultimate fighters, the Hunter was never exposed to combat as were the Mig or Sabre, yet it outlasted them both and stayed in front line service longer.

The Hunter's potential in combat was never fully realised

Operated by no less than 19 countries, the Hunter spent almost 50 years in active front line service but never achieved the title of being a Great Combat Aircraft. Although it saw limited action in a number of conflicts it never became embroiled in such classic air battles as those of WW2 or Korea and hence while it had the potential to have been a great dogfighter, it never had the opportunity to prove it.

The WW2 Boeing B-17 Flying Fortress, however, undoubtedly wears the title of a Great Combat Aircraft. While not the most technically advanced aircraft of its day, nor the biggest load carrier or even the bomber with the longest range, it is undeniably a Great Airplane.

12,732 B-17s were produced. 4,735 were lost during WW2. Another contender for the title of Greatest Combat Aircraft of all Time

There's also many other aircraft that haven't seen combat yet may still qualify for the title of Great. One contender is Lockheed's Constellation. Speak to any veteran aviation enthusiast who was around in the heyday of the "Connie" and they'll go bleary eyed with emotion about the beautiful lines of this classic propellor driven aircraft. Emotion aside, the Constellation introduced many innovations that later became standard for passenger aircraft - including pressurisation and weather radar. Developed before WW2, production stalled until the war's end. After the war it bridged the gap between the last piston engined liners and the new generation of jets. It also saw service in military guise as the EC121 AWACs platform. However it's difficult to define why the aircraft earns the title of Great, yet try arguing that it's not a great plane with any Constellation supporter. Perhaps being one of the most graceful aircraft ever flown is sufficient to earn the title, although aesthetics alone shouldn't be the primary criteria.

Clean lines made the Connie the fastest passenger liner of the time. The EC-121 version qualifies it as a combat aircraft.

So in this series when we compare aircraft, it isn’t our intention to suggest that one is “greater” than another, simply because it flew faster, further or carried a heavier bomb load or shot down more of its opponents than any other type. Often the reasons are elusive, however if they’ve earned the title of Great Aircraft - combat or otherwise, it’s because of many factors, including the deeds of the crews that flew them, the missions large and small, and a thousand other factors, all of which when combined add up to that almost indefinable quality known as Greatness.