In general, an aircraft flight so planned and navigated as to take advantage of the flight-altitude winds (pressure pattern) to reduce flying time. As techniques have advanced, this concept has become increasingly referred to as minimal flight. Probably the most widely used method today is based upon the determination of D-values with pressure and radio altimeters while in flight. This provides for the continual adjustment of flight course to take fullest advantage of winds in long flights over water. Flight plans made out by the navigator are based on meteorological forecasts of wind distribution. These forecasts are usually prepared in the form of maps analyzed in terms of D-values at the flight pressure altitude. During flight, observations of actual D-values can conveniently be used to make relatively small corrections. See constant-pressure-pattern flight, aerologation, single-heading navigation, 4-D chart, wave-front method, single drift correction, multiple drift correction.