A powerful Delta 4 Heavy rocket carrying a U.S. spy satellite lifts off from Vandenberg Air Force Base in Calif., Saturday, Jan. 19, 2019. The rocket propelled the National Reconnaissance Office satellite at 11:10 a.m. Pacific time, arcing over the Pacific Ocean west of Los Angeles as it headed toward space. The United Launch Alliance Delta 4 Heavy is made up of 3 rocket cores strapped together producing almost 2.2 million pounds of thrust at lift-off. (AP Photo/Matt Hartman)
camera (The Associated Press) A powerful Delta 4 Heavy rocket carrying a U.S. spy satellite lifts off from Vandenberg Air Force Base in Calif., Saturday, Jan. 19, 2019. The rocket propelled the National Reconnaissance Office satellite at 11:10 a.m. Pacific time, arcing over the Pacific Ocean west of Los Angeles as it headed toward space. The United Launch Alliance Delta 4 Heavy is made up of 3 rocket cores strapped together producing almost 2.2 million pounds of thrust at lift-off. (AP Photo/Matt Hartman)

A powerful Delta 4 Heavy rocket carrying a U.S. spy satellite lifted off Saturday from California.

The rocket propelled the National Reconnaissance Office satellite from Vandenberg Air Force Base at 11:10 a.m. Pacific time, arcing over the Pacific Ocean west of Los Angeles as it headed toward space.

The outer boosters of the rocket separated about four minutes into flight, followed shortly by separation of the central first-stage booster and successful ignition of the upper stage.

As is customary with classified payloads, United Launch Alliance webcast the liftoff only until the aerodynamic fairing covering the payload was discarded.

Details of the mission, dubbed NROL-71, were not released.

The launch had been repeatedly delayed since late last year for various reasons including a hydrogen leak, high winds and a problem with ground communication equipment.

The National Reconnaissance Office is responsible for U.S. intelligence satellites.

United Launch Alliance is a joint venture of Lockheed Martin and Boeing.

The Delta 4 Heavy stands 233 feet (71 meters) tall.