The demonstration launch of the Boeing Delta 4 Heavy rocket was pushed back 24 hours to Dec. 11 due to adverse weather conditions, including ground winds, clouds and isolated thunderstorm in the vicinity of the pad and the rocket’s flight path, that were expected at Cape Canaveral Air Force Station in Florida today.

The 2 hour, 56 minute launch window on Dec. 11 opens at 2:31 p.m. EST.