Bomber Command had tried to attack German forces in daylight during the Norway campaign and suffered very heavy losses resulting in the decision to only use bombers at night (the exception during the French campaign again showed the futility of attacking without numerical superiority). Therefore, when combined with navigation problems of finding targets at night, Bomber Command was restricted to attacks on the channel ports and communications centres (which they usually missed by miles). Mass attacks on German airfields was therefore not an option - especially since we did not have the masses at the time.