To our pleasant surprise, this airplane was almost as fast at 24,000 feet as the much-more-expensive C-340. No doubt its large wing area and lighter gross weight had a lot to do with its impressive speed at that altitude. At 20,000 feet the published maximum cruising speed is 230 mph as compared to 241 mph for the C-340. Those engines are rated at 225 and 285 hp, respectively.

Changes in 1974 were an improved airstair door lift, gear accumulator, and improved rocker switches. The 1975 versions featured 148-gallons of usable fuel as standard, and an optional Skymaster II package along with a full flap extension speed of 110 knots and a 1/3 extension at 165 knots. In 1977 an avionics master switch was included and an optional weather radar system was offered. In the 1978-80 model years only minor interior refinements were made, and with a list price of $178,070 in 1980, the production line was halted. That price was only $78,500 when production started in 1973. But this had become quite an airplane in the intervening years. With all of the optional equipment for allweather flying some of the airplanes were delivered at a retail price exceeding $250,000. Total domestic deliveries were 140 units in 1973, 40 units in 1974, 30 units in 1975, 40 units in 1976, 30 units in 1977, 25 units in 1978, 23 units in 1979 and only 15 units in 1980. The Reims, France plant built 23 FP337's from 1973-80.

To the author's knowledge the airplanes have held up quite well through the years. The one exception would be the difficulty in maintaining an air-tight cabin. In fact, that was also a frequent task in production flight tests where leaks had to be located and plugged. If leaks were excessive, the pressurization system would be incapable of maintaining the 3.35 psi cabin pressure differential with 40% engine power in descents from high altitudes. Thus more power would be needed in long descents.