Beirne Lay Jr., 72, a former military pilot and an author and screenwriter whose films include "Twelve O'Clock High," one of the most highly regarded movies about World War II ever made, died of cancer May 26 at a hospital in Los Angeles. He lived in Brentwood, Calif.

Military flying provided the material for the books and films for which Mr. Lay is best remembered. Born in Berkeley Springs, W. Va., Mr. Lay was commissioned a pilot in the Army Reserves in 1932 just after graduating from Yale. In World War II, he served briefly in Washington and then went to England as a pilot flying four-engined Liberator bombers. He was shot down over France in 1944.

An account of the incident in The Washington Post said Mr. Lay, then a lieutenant colonel, was leading a bombing raid when enemy flak knocked out two engines. When a third engine failed and the controls stuck, he ordered his men to parachute. The newspaper account said other flyers on the mission "watched the men land and reach cover before they were attacked by enemy fighters." Mr. Lay spent the rest of the war being hidden from the Germans by the underground.

In 1946, he resigned from the service with the rank of colonel and moved to California. His decorations included the Distinguished Flying Cross and the Purple Heart.

In the 1930s, Mr. Lay had written "I Wanted Wings," which was made into a movie. Out of his war experiences came "Presumed Dead," an account of being shot down and evading capture, and the novel and film "Twelve O'Clock High," of which Sy Bartlett was the coauthor. The movie was released in 1949 and starred Gregory Peck.

It is the story of a bomber group whose casualties are high and whose efficiency is low. Its commander is not hard enough in matters of training and discipline. Frank Savage, a veteran officer played by Peck, is put in command for the purpose of bringing it up to the mark. The film explores discipline, sacrifice, danger and the limits of human endurance. Savage accomplishes his mission but only at the cost of a breakdown himself.

In the 1960s, Mr. Lay converted "Twelve O'Clock High" into a television series.

Mr. Lay earned Academy Award nominations for two later screenplays, "Above and Beyond," (1953) and "Strategic Air Command" (1954). His other television credits include "Combat" and "The Barbara Stanwyck Theatre."

Survivors include his wife, Philippa Ludwell Lay, and two daughters, Philippa Lay and Frances Lay, all of Brentwood, Calif., and two sisters, Sophie McClanahan of California and Louisa Morton of Warsaw, Va.