The prototype Spitfire (K5054) was flown unpainted by chief test pilot 'Mutt' Summers at Eastleigh airfield (now Southampton airport) on March 5th 1936. The Spitfire Mk.I reached No.19 Squadron at Duxford in July 1938. The Mk.1 Spitfire had a 1,030-hp Merlin II engine and eight Browning 0.303-in machine guns. In early 1940 the Mk.IB was delivered which had a superior armament of two 20-mm cannon and four 0.303-in machine guns. Subsequent variants improved engine power, firepower, and strengthened airframes. Variants included fighters, high altitude interceptors, low level interceptors, Photo Reconnaissance aircraft at high and low level, and even a navalized version called the Seafire.

The Mk.V Spitfire had a strengthened fuselage, a more powerful Merlin engine of 1,440-hp or 1,470-hp with drop tank and provisions for a 500 Ib bomb. The armament varied with either eight 0.303-in machine guns, two cannons and four machine guns, or four cannons. Spitfires designed to operate at low level had the tips of their wings removed to improve manoeuvrability and speed at low level. No fewer than 6,479 Spitfire Vs were built, more than any other mark.

The Mk.IX Spitfire was also built in large numbers with a total of 5,665 aircraft produced. In fact the Mk.IX was simply a Mk.V Spitfire with a newer engine. The Spitfire Mk.VIII was a much better aircraft and in the opinion of most pilots the nicest of all Spitfires to fly and yet far fewer were built.

The Mk.XIV was the most important Spitfire in the final year of World War 2. It had a two-stage Griffon engine delivering 2,050-hp and driving a five bladed propeller. The airframe was redesigned and strengthened with symmetric deep radiators, broad tail and often a teardrop canopy. A total of 957 of these aircraft were built.

Spitfire I:
Original production model with 1,030-hp Merlin II engine, 8 Browning 0.303-in guns (Mk IB had 2 20-mm cannons and 4 0.303-in machine guns), Total aircraft 1,566.

Spitfire II:
Castle Bromwich aircraft with small changes and 1,175-hp Merlin XII engine, Total aircraft 750 IIA and 170 IIB.

Spitfire III:
Experimental prototype with 1,280-hp Merlin XX engine, Total aircraft 1.

Spitfire IV:
Griffon engined prototype

Spitfire V:
Strengthened fuselage for 1,440-hp Merlin 45 or 1,470-hp Merlin 50, drop tank and bomb provisions, A (8 machine guns), B (2 cannon & 4 machine guns), or C (4 cannons) armament, Total aircraft 94 VA, 3,923 VB, and 2,447 VC.

Spitfire VI:
High altitude intercepter with 1,415-hp Merlin 47, pressurized cockpit and pointed wings, Total aircraft 100.

Spitfire VII:
High altitude intercepter with 2 stage Merlin 61, 64 or 71, pressurized cockpit, retractable tailwheel, often broad pointed rudder, Total aircraft 140.

Spitfire VIII:
Definitive fighter with 2 stage Merlin 61, 63, 66, or 70, unpressurized, Total aircraft 1,658.

Spitfire IX:
Temporary stop-gap, marriage of 2 stage Merlin 61, 63, 66, or 70 with Mk.V airframe, B, C, or E (2 cannons & 2 0.5-in machine guns) armament, Total aircraft 5,665.

Spitfire X:
Pressurized version of PR.XI, Merlin 77, Total aircraft 16.

Spitfire XI:
Unarmed reconnaissance aircraft, Merlin 61, 63, or 70, Total aircraft 471.

Spitfire XII:
Low level intercepter, single stage Griffon II or IV of 1,735-hp, B armament, Total aircraft 100.

Spitfire XIII:
Low level PR aircraft based on Mk.V but with Merlin 32 (3 blade prop), Four 0.303-in machine guns only, Total aircraft 18.

Spitfire XIV:
2 stage Griffon 65 or 66 of 2.050-hp driving 5 blade propeller and redesigned & strengthened airframe with symmetric deep radiators, broad tail, and often teardrop canopy, C or E armament, Total aircraft 957.

Spitfire XVI:
Mk.IX with Packard Merlin 266, usually C or E armament, many with teardrop canopy, Total aircraft 1,054.

Spitfire XVIII:
Definitive fighter with 2 stage Griffon, E armament, teardrop canopy, extra wing fuel, FR.XVIII (postwar FR.18) with rear fuselage reconnaissance camera, Total aircraft 300.

Spitfire XIX:
Unarmed PR version, 2 stage Griffon, most pressurized, Total aircraft 225.

Spitfire XX:
Prototype rebuilt from Mk.IV and prototype Mk.XII, Total aircraft 225.

Spitfire 21:
Redesigned airframe, mainly Griffon 61 or 64 driving five bladed propeller, Four 20-mm guns, Total aircraft 122.

Spitfire 22:
Minor changes, some with 2,375-hp Griffon 85, and contraprop Total aircraft 278.

Spitfire 24:
Minor changes, Spiteful tail, short barrel Mk.V cannon, Total aircraft 54.

Seafire IB:
Navalized Spitfire VB Total aircraft 166.

Seafire IIC:
Catapult hooks and strengthened landing gear, Merlin 32 engine driving four blade propeller, Total aircraft 372.

Seafire III:
Double folding wing, 1,585-hp Merlin 55M engine, Total aircraft 1,220.

Seafire XV:
Single stage 1,850-hp Griffon VI and asymmetric radiators as Spitfire XII, Most with sting hook, Late production teardrop canopy, Total aircraft 390.

Seafire XVII or 17:
As Seafire XV with teardrop canopy, often strengthened landing gear, Some (FR.17) with camera in place of rear tank, Total aircraft 232.

Seafire 45:
Same new airframe as Spitfire 21, Non folding wing, Griffon 61 (5 blade prop), or 85 (contraprop), Total aircraft 50.

Seafire 46:
As Seafire 45, teardrop canopy, FR.46 with rear fuselage camera, Late production Spiteful tail, Total aircraft 24.

Seafire 47:
Folding wing (most hydraulic), 2,375-hp Griffon 87 or 88 with contraprop and carburettor air inlet just below spinner, Increased fuel, Late production all FR type with camera, Total aircraft 140.