restrictions, but agreed to cooperate with the investigation to the fullest extent. The following day, the Agency reversed course, and said that the Electra airliners could resume normal operation if they replaced the new altimeters with old-style altimeters. Both airlines agreed to immediately replace the altimeters as a precautionary step. The Agency also extended the order to include the requirement that new-style altimeters that had been installed in Boeing 707 aircraft needed to be replaced. The altimeters used in the aircraft had been an early focus of the investigation. The units that Lockheed had used in its Electra turboprops were a different style than what had been used in older piston-type aircraft. The older type used three hands of different lengths to indicate the aircraft's altitude, but the new design combined an analog gauge with graduations indicating hundreds of feet, and a rectangular display with numbers printed on rotating drums that indicated the thousands of feet. The Kollsman Instrument Corporation, which built both types, described the new style as a "precision drum altimeter" and said that it had been "developed as a result of a human engineering study made by the Aero Medical Laboratory, by an unnamed government body, and at the instigation of the Air Force, primarily to meet the needs of faster flying." The Air Force had reported multiple cases where its pilots had misread the older-style altimeters and had misinterpreted their altitude by 10,000 feet. On the other hand, pilots training on newer aircraft reported several instances where they had misread the altitude on the new-style altimeters, causing them to misread the aircraft's altitude by up to 1,000 feet. Because of the confusion, early reports said that the airline had made plans to install an additional third altimeter of the old type in the center of the pilot's panel while continuing to use the newer style altimeters. Pilots for Eastern Airlines who had been flying the Electra aircraft also complained about the new style of altimeter, stating that not only were they easy to misinterpret, but they tended to lag behind the older style. That airline had installed a third, old-style, altimeter in their cockpits. American Airlines defended the new style altimeter as "a new and far superior altimeter with finer gradations" and denied that it had received complaints with the instruments. It acknowledged that it had planned to install a third altimeter in the center of