Engines grow in power with development, but a major war demands the utmost performance from engines fitted to aircraft whose life in front-line service was unlikely to exceed 50 hours' flying, over a period of only a month or two. In peacetime however, the call was for reliability over a period of perhaps a dozen years, and the R-2800's reliability commended its use for long-range patrol aircraft and for the Douglas DC-6, Martin 4-0-4, and Convair 240 transports. The last two were twin-engine aircraft of size, passenger capacity, and high wing loading comparable to the DC-4 and the first Constellations.[4]