aerial survey companies and employed for mapping. From the 1950s on, the use of the Lightning steadily declined, and only a few more than two dozen still exist, with few still flying. One example is a P-38L owned by the Lone Star Flight Museum in Galveston, Texas, painted in the colors of Charles H. MacDonald's Putt Putt Maru. Two other examples are F-5Gs, which were owned and operated by Kargl Aerial Surveys in 1946, and are now located in Chino, California, at Yanks Air Museum, and in McMinnville, Oregon, at Evergreen Aviation Museum. The earliest-built surviving P-38, Glacier Girl, was recovered from the Greenland ice cap in 1992, 50 years after she crashed there on a ferry flight to the UK, and after a complete restoration, flew once again 10 years after her recovery. Production Over 10,000 Lightnings were manufactured, becoming the only U.S. combat aircraft that remained in continuous production throughout the duration of American participation in World War II. The Lightning had a major effect on other aircraft; its wing, in a scaled-up form, was used on the Lockheed Constellation. P-38D and P-38Es Delivered and accepted Lightning production variants began with the P-38D model. The few "hand made" YP-38s initially contracted were used as trainers and test aircraft. No Bs or Cs were delivered to the government as the USAAF allocated the 'D' suffix to all aircraft with self-sealing fuel tanks and armor. Many secondary but still initial teething tests were conducted using the earliest D variants. The first combat-capable Lightning was the P-38E (and its photo-recon variant the F-4) which featured improved instruments, electrical, and hydraulic systems. Part-way through production, the older Hamilton Standard Hydromatic hollow steel propellers were replaced by new Curtiss Electric duraluminum propellers. The definitive (and now famous) armament configuration was settled upon, featuring four .50 in (12.7 mm) machine guns with 500 rpg, and a 20 mm (.79 in) Hispano autocannon with 150 rounds. While the machine guns had been arranged symmetrically in the nose on the P-38D, they were "staggered" in the P-38E and later versions, with the muzzles protruding from the nose in the relative lengths of roughly 1:4:6:2. This was done to ensure a straight ammunition-belt feed into the weapons, as the earlier arrangement led to jamming. The first P-38E rolled out of the factory in October 1941 as the Battle of Moscow filled the news wires of the world.