This was in 1945 while advising Jay Forrester in developing flight simulators and anti-aircraft fire control devices during World War II, before practical digital computers had been produced.

[4] When his father became president of American Utilities Service Corporation in Chicago, Crawford attended New Trier Township High School in Winnetka, Illinois.

[5] He entered the Massachusetts Institute of Technology in 1936 to study electrical engineering and came to work under Vannevar Bush with fellow student Claude Shannon on the differential analyzer.

[10] From 1942 to 1945 Crawford served as a civilian attached to the Navy's Special Devices Section (a predecessor of the Naval Air Warfare Center Training Systems Division) at Sands Point, Long Island.

Crawford supervised the Navy Ballistics Computation Program until September 1948 when he accepted a temporary position  with the Research and Development Board of the Department of Defense.

[11] As head of the computer section in ONR he came into contact with Jay Forrester at MIT who, with his collaborator Robert Everett (computer scientist), headed a project that had roots in developing flight simulators for pilot training and evolved into the Whirlwind Project which in turn prepared the way for the air-defense application SAGE (Semi-Automatic Ground Environment).

In the fall of 1947, following conversations with Perry Crawford, we wrote two documents, numbered L-1 and L-2, that showed how digital computers could manage a Naval task force and interpret radar data.

[13]Crawford also contributed to the Moore School Lectures with a talk entitled "Applications of Digital Computation Involving Continuous Input and Output Variables" (August 5, 1946).

in 1954 Thomas J. Watson, Jr., son of IBM's founder, oversaw Crawford's placement, along with Hans Peter Luhn, to head the design team for creating a digital computer system for managing American Airline's reservations and ticketing.

[16] Named SABRE (Semi-Automatic Research Environment), it soon grew to managing the total operation: flight planning, crew schedules, special meals, etc.The project was at the time easily the largest civilian computerization task ever undertaken, involving some 200 technical personnel producing a million lines of program code.

By the early 1970s all the major carriers possessed reliable real-time systems and communications networks that had become an essential component of their operations, second in importance only to the airplanes themselves.