The Admiralty takes control

On May 24th 1939 administrative control of the Fleet Air Arm, the naval aviation wing of the Royal Navy, was transferred to the Board of Admiralty from the Royal Air Force under the "Inskip Award". Formed on April 1st 1924 the Fleet Air Arm encompassed all RAF aircraft that operated from carriers and other fighting ships. Renamed the Air Branch of the Royal Navy, at the onset of the Second World War, the Fleet Air Arm consisted of only 20 squadrons and 232 aircraft.

Squadrons were to be numbered in two blocks – 800 – 899 for first-line and 700-799 for second-line units; once these numbers were exhausted 1700 and 1800 series numbers were allocated.  Squadron numbers in further divided into blocks, organised by type and function:

First Line Squadrons

Nos.800 to 809 Single-seat fighter squadrons in carriers.Nos.810 to 819 Torpedo bomber squadrons in carriers, later torpedo spotter reconnaissance and torpedo bomber reconnaissance squadrons.
Nos.820 to 859 Spotter reconnaissance squadrons, later torpedo spotter reconnaissance and torpedo bomber reconnaissance squadrons.
Nos.860 to 869 Torpedo bomber reconnaissance squadrons. Later reserved for Dutch-manned and then Dutch Navy squadrons.
Nos.870 to 879 Single-seat fighter squadrons. Later reserved for Royal Canadian Navy use.
Nos.880 to 899 Single - seat fighter squadrons in carriers.
Nos.1700 to 1749 Torpedo bomber reconnaissance squadrons, reallocated to amphibian bomber reconnaissance squadrons.
Nos.1750 to 1769 Single-seat fighter squadrons (not taken up).
Nos.1770 to 1799 Two-seat fighter squadrons.
Nos.I800 to 1809 Torpedo bomber reconnaissance squadrons (not taken up)
Nos.1810 to 1829 Dive-bomber squadrons.
Nos.1830 to 1899 Single-seat fighter squadrons.

Second Line Squadrons

Nos.700 to 749 initially for Catapult flights, later becoming catapult squadrons. When these ceased to exist the range became available for training and ancillary squadrons.

Nos.700 to 710 were earmarked for use by amphibian and floatplane squadrons in 1943, but this later lapsed.

Nos.750 to 799 Training and ancillary squadrons.
 

Reserve Squadron

Nos.1830 to 1844 Used for Royal Naval Volunteer Reserve squadrons, and latterly RNR squadrons.