Improved structural design criteria for gust loads on aircraft are presented based on the continuous turbulence concept and probabilistic considerations. It is proposed that these improved criteria may replace the heretofore used discrete gust concept. The improved criteria consist of a rational-probability analysis backed up by a design envelope analysis. Both of these analyses are related to the strength level of a previously successful commercial transport and employ power spectral density techniques to establish design values. In conjunction with the rational-probability analysis, an acceptable failure probability is specified, and, for the design envelope analysis, a design limit gust velocity is established. Finally, the turbulence field parameters that may be used for design calculations on new aircraft are specified.