To attack England, the Luftwaffe brought together 1,800 bombers and 1,000 fighters in 3 air fleets:Luftwaffe V, based in Norway (to launch diversionary operations in the northeast), Luftwaffe II, based in Holland , in Belgium and France north of the Seine, and the Luftwaffe III, based in Brittany and Lower Normandy. The best German fighter is the Me-109, but its range is too short (it can only stay 10 minutes above London) so the Germans plan to have their bombers protected by the Me -110. It can stay in the air longer, but it is so unwieldy that it is unable to effectively protect the bombers - unless it is itself "covered" by formations of Me-109s. On the bombardment side, the situation is not much better:all the Luftwaffe bombers (Ju-88, He-111, Do-17J have too short a range of action, and none can carry more than 2 tons of bombs As for the Ju-87 Stuka, designed for the dive bombing of cities and communication routes, it is so disappointing in combat that it will be quickly withdrawn from all operations involving an encounter with enemy fighters. of the Luftwaffe are therefore its numerical superiority, the superiority of the defensive armament of its fighters (at least during the first weeks of the battle) and the fact that its flight bases occupy an immense arc of a circle going from Narvik to Brest To the 3,000 German aircraft, the British Fighter Command (fighter command) can oppose only 850 hunters, divided into 4 groups:group 13 (Scotland), group 12 (Center), group 10 (South-West ) and group 11 (South-East), which must support the g ros of the offensive. R.A.F. are the Hurricane and the Supermarine Spitfire. Too slow for the Me-109s, the Hurricanes were assigned to bomber attacks, but the Spitfires, fast and manoeuvrable, armed with 8 wing machine guns, operating in their own airspace, with greater autonomy than the German fighters, are perfectly adapted to their defensive mission. On the other hand, Great Britain was in 1940 the only country in the world with anti-aircraft protection, a network of radar stations at high altitude and long range (5,000 m-200 km), coastal stations at low altitude and medium range ( 200m-100km), Coastal Command ground observers (coastal defense) and passive defense. The combined use of these different elements, which allows Fighter Command to economize its forces by employing them only with certainty, partly compensates for the numerical inferiority of the R.A.F. But only partly, because if the British aeronautical industry produces enough apparatuses to reconstitute without difficulty the decimated squadrons, the pilots killed in combat cannot be replaced at short notice, and the lack of specialized personnel risks paralyzing short or in the medium term the English hunt.
When Hitler asked the Luftwaffe on August 2 to move into the active preparation phase of Operation Sea Lion, the plan for the attack had been carefully laid out. The offensive was to begin on the “Day of the Eagle” (Adlertag) with a massive outing of German bombers and fighters. In 4 days, the British fighter must be destroyed, pinned down or driven north, then 4 weeks of heavy bombardment must disrupt Britain's economy and defences. If this schedule is respected, the aerial operations will therefore be completed 1 month and 4 days after the "Day of the Eagle", set for August 13, i.e. September 17 - the deadline set for the start of Operation Sea Lion.
On August 13, the Luftflotten II, III and V went into action, but the coordination of the raids was poor, the objectives were poorly located, Fighter Command repelled all attacks. On the 14th, bad weather grounded the German planes. On the 15th, the offensive is general. The Luftwaffe carried out 2,000 sorties, launching over Great Britain more than 1,000 aircraft on a front of 800 km. Luftflotte V, whose formations must cross the North Sea, suffered 20% losses, which virtually eliminated it from the battle. The R.A.F. performs 974 sorties and loses 35 aircraft (for 80 German aircraft shot down). From the 16th to the 18th, the Luftflotten II and III maintain their pressure, but without managing to saturate the English defences. For every 100 British aircraft shot down, the Luftwaffe loses 375 bombers and 100 fighters. Me-110s and Ju-88s are easily outclassed by Spitfires, and Hurricanes inflict severe casualties on He-111 formations. The Me-109s could restore the balance, despite their low range, but Goering persists in confining them to bomber protection missions that reduce their effectiveness.