[1] He enlisted in the Royal Canadian Air Force in January 1941, and received his pilot's wings in September the same year.

Commissioned in 1942, Flight Lieutenant Hornell completed 60 operational missions, involving some 600 hours flying.

On 24 June 1944 on sea patrol near the Faroes in the North Atlantic, Hornell's aircraft was attacked and badly damaged by the German submarine U-1225.

[3] Flight Lieutenant Hornell was captain and first pilot of a twin-engined amphibian aircraft engaged on an anti-submarine patrol in northern waters.

The patrol had lasted for some hours when a fully-surfaced U-boat was sighted, travelling at high speed on the port beam.

Nevertheless, the captain decided to press home his attack, knowing that with every moment the chances of escape for him and his gallant crew would grow more slender.

With the utmost coolness, the captain took his aircraft into wind and, despite the manifold dangers, brought it safely down on the heavy swell.

The men struggled vainly to reach it and Flight Lieutenant Hornell, who throughout had encouraged them by his cheerfulness and inspiring leadership, proposed to swim to it, through he was nearly exhausted.

By pressing home a skilful and successful attack against fierce opposition, with his aircraft in a precarious condition, and by fortifying and encouraging his comrades in the subsequent ordeal, this officer displayed valour and devotion to duty of the highest order.

[5] The Canso aircraft in the collection of the Canadian Warplane Heritage Museum in Hamilton, Ontario, was restored in the colours and markings of 162 (Bomber Reconnaissance) Squadron and dedicated to the memory of Flight Lieutenant David Hornell, VC.

[6] A squadron of the Royal Canadian Air Cadets in the west end of Toronto, Ontario, is named after him.