During World War II it was a fighter squadron and is notable for having fought in the Battle of Britain.

1 Squadron Royal Canadian Air Force was formed as a fighter unit at Trenton, Ontario, on 21 September 1937 with Siskin aircraft.

In August 1938, the squadron moved to Calgary, Alberta, and was re-equipped with Hawker Hurricane aircraft in February 1939.

It was mobilized at Saint-Hubert, Quebec, on 10 September 1939, and on 5 November 1939 it moved to Dartmouth, Nova Scotia.

It had brought its own Hurricanes from Canada, and as these were not fully up to UK standard, the squadron was non-operational until mid-August when it moved to RAF Northolt.

The squadron's début was inauspicious when two Bristol Blenheims of RAF Coastal Command were accidentally shot down on 24 August, and three crewmen killed.

However, three of the squadron's aircraft were shot down and one pilot (Flying Officer R. L. Edwards[6]) was killed.

On 11 October the depleted squadron was moved to RAF Prestwick in Scotland and its operational activity was coastal patrol work over the Clyde approaches.

It flew 1,694 sorties (1,569 operational hours and 1,201 non-operational), lost three pilots killed, thirteen wounded, 17 aircraft FB/Cat.

Based at Biggin Hill, flying Spitfires, the squadron was on escort duties to a bomber raid over France on 5 June 1942 when he was shot down and killed.

On 21 October 401's first loss of this phase of operations was Flight Sergeant B.F. Whitson, taken prisoner after being shot down over Saint-Omer.

On 27 October the squadron was operating as high cover to the Biggin Hill Wing, and were 'bounced' by I and III Gruppe, JG 26, led by Oberst Adolf Galland.

[10] On 8 November 1941 on the last mass fighter sweep of the year the squadron was attacked by I. and III./JG 26, and Flying Officer J. C. Weir (prisoner of war) and Sergeant R. W. Gardner (killed) were lost over Le Touquet shot down by Fw.

The escort missed the rendezvous, however, although 401 later claimed two Bf 109s destroyed, for the loss of Sergeant Levesque, who was taken prisoner.

On 1 May the squadron lost two more Spitfires to JG 2 over Le Havre while, on 1 June 1942, when a section of 401 intercepted and shot down two Hawker Typhoon fighters of No.

In June the squadron received some of the first Mark IX Spitfires, capable of taking on the Focke Wulf Fw 190A on more or less equal terms.

On 8 November Flight Lieutenant Don Morrison was shot down and badly wounded versus units of JG 26, losing a leg and being repatriated in 1943.

On 29 September the squadron surprised some thirty Bf 109s attacking a Typhoon formation, and claimed at least nine destroyed for one loss.

[5] On 5 October, a five-strong squadron patrol encountered a Messerschmitt Me 262 jet of KG 51 and shot it down, the pilot, Hpt.

In the course of Operation Bodenplatte, the mass ground-attack of 1 January 1945 by the Luftwaffe, the unit claimed nine of the attackers shot down, making the tally since D-Day 76.5 aircraft destroyed, three probables and 37 damaged.

The squadron caught Fw 190s taking off from Twente airfield on 14 January and five fighters of I./JG 1 shot down for one loss, Flight Lieutenant L. J. Mackay claiming three.

The squadron ended the war as 2TAF's top scoring unit, claiming 112 aerial victories between 6 June 1944 and 5 May 1945.

The squadron flies the CF-18 Hornet, Canada's primary and front-line jet fighter aircraft.