The problems experienced in the heavy bomber supply diplomacy of 1941 indicated that the British ability to overcome resistance from the USAAF to their supply objectives was already strongly limited before the American entry into the war. Another factor involved in that diplomacy was the dominant influence of quality in terms of aircraft performance by type and in their operational equipment. Both these features were to come together in an unexpected fashion in the fighter supply diplomacy of 1941–2 which culminated in the negotiations to conclude the second Arnold–Towers–Portal agreement of June 1942.

Though the first ATP agreement of January 1942 had appeared to confirm a reduced British position in aircraft supply allocations, the pressure the USAAF faced in the following six months led to a further renegotiation at British expense and against British protest. This pressure was due to demands of equipping and deploying USAAF combatant units alongside the continuing demands of Allied supply, and against a continuing background of insufficient production. This was a familiar enough story but what made the situation particularly interesting, with regard to the supply of fighter aircraft in 1942, was the extent of this pressure and the British response to it.