In March 1940, the France and the United Kingdom, through the British Purchasing Commission, ordered a total of 667 P-38s for US$100M, designated Model 322F for the French and Model 322B for the British. The aircraft would be a variant of the P-38E. The overseas Allies wished for complete commonality of Allison engines with the large numbers of Curtiss P-40 Warhawk both nations had on order, and thus ordered the Model 322 twin right-handed engines instead of counter-rotating ones and without turbo-superchargers. Performance was supposed to be  at . After the fall of France in June 1940, the British took over the entire order and gave the aircraft the British military aircraft designation systems "Lightning." By June 1941, the War Ministry had cause to reconsider their earlier aircraft specifications based on experience gathered in the Battle of Britain and The Blitz. British displeasure with the Lockheed order came to the fore in July, and on 5 August 1941 they modified the contract such that 143 aircraft would be delivered as previously ordered, to be known as "Lightning (Mark) I," and 524 would be upgraded to US-standard P-38E specifications with a top speed of  at  guaranteed, to be called "Lightning II" for British service. Later that summer an RAF test pilot reported back from Burbank with a poor assessment of the "tail flutter" situation, and the British cancelled all but three of the 143 Lightning Is. As a loss of approximately US$15M was involved, Lockheed reviewed their contracts and decided to hold the British to the original order. Negotiations grew bitter and stalled. Everything changed after the 7 December, 1941 attack on Pearl Harbor after which the United States government seized some 40 of the Model 322s for West Coast of the United States defense; subsequently all British Lightnings were delivered to the USAAF starting in January 1942. The USAAF lent the RAF three of the aircraft, which were delivered by sea in March 1942 and were test flown no earlier than May at Cunliffe-Owen Aircraft Swaythling, the Aeroplane and Armament Experimental Establishment and the Royal Aircraft Establishment. The A&AEE example was unarmed, lacked turbochargers and restricted to ; though the undercarriage was praised and flight on one engine described as comfortable. These three were subsequently returned to the USAAF; one in December 1942 and the others in July 1943. Of the remaining 140 Lightning Is, 19 were not modified and were designated by the USAAF as RP-322-I (R for Restricted, because non-counter-rotating propellers were considered more dangerous on takeoff), while 121 were converted to non-turbo-supercharged counter-rotating V-1710F-2 engines and designated P-322-II. All 121 were used as Trainer (aircraft); a few were still serving that role in 1945. A few RP-322s were later used as test modification platforms such as for smoke-laying canisters. The RP-322 was a fairly fast aircraft below  and well-behaved as a trainer.. How many months after the aircraft were delivered to RAF were they test flown at Cunliffe-Owen Aircraft Swaythling?