 Over US$120 million was spent to develop the base in the 1940s and expand it to .The base's main runway was completed in a single pour of concrete.On the afternoon of 7 December 1941, the 41st Bombardment Group and the 6th Reconnaissance Squadron moved to Muroc from Davis-Monthan Army Airfield, Arizona, with a collection of B-18 Bolos, B-25 Mitchells, and an A-29 Hudson.