The Battle of Britain Five Months That Changed History, May—October 1940 by James Holland (z-lib.org).epub

However, because of its greater share of the rearmament cake, the RAF
had nonetheless been obliged to make proportionally more of a contribution
in the air than on the ground in France. The organization of the RAF forces
in France was horribly complicated. Unlike the Luftwaffe, which was
divided rather like ground forces, but into Air Fleets and Air Corps
consisting of a mixture of aircraft, the RAF was divided into three homebased
commands: Bomber, Fighter and Coastal. The problem was that
aircraft for France had to be drawn from those commands and then placed
in a new set-up, known as the British Air Forces in France. This was in turn
then split in two. The BEF Air Component consisted of thirteen squadrons
of Lysanders and Blenheims for reconnaissance, and Hurricanes for
protection, and was to directly support the army, and so came under the
control of General Gort. The Advanced Air Striking Force (AASF), on the
other hand, was independent of both Gort and the French and was
commanded by Air Vice-Marshal Playfair, answerable to Bomber
Command HQ back in England. Should Gort want stronger bomber support
than could be provided by the Air Component, he had to apply to the War
Office back in London, who would then ask the Air Ministry, who in turn
would order Bomber Command. They would then command AVM Playfair.
It was hardly a system that encouraged the kind of quick response so often
needed in the heat of battle.
There were around 500 front-line British aircraft on the morning of 10
May, although, as with the Armée de l’Air, there were more waiting in the
wings – not least four more fighter squadrons that had been promised from
the UK the moment an offensive started, and a bomber group from Bomber
Command operating from England that had been put under command of the
AASF.
Like everyone on the Allied side, the air forces had been expecting the
offensive to begin sooner rather than later. At Senon airfield north-west of
Verdun, however, the two squadrons at the airfield, 87 Fighter Squadron
and 2 Squadron of Lysander reconnaissance planes, had been given
something of a warning on the night of 9 May, when the Headquarters of
the French air force’s Operations Zone (North) received intelligence that
Luftwaffe attacks were expected at dawn. Given the task of covering the
northern part of the Maginot Line, these two squadrons had been
temporarily severed from the rest of the RAF units in France and placed in