Stats: Atlas 5 and Delta 4 histories and backlogs (updated April 20)

The 8-million-pound mobile service tower is retracted from around the Atlas 5 rocket, revealing the 20-story-tall vehicle for liftoff from Vandenberg Air Force Base, California.

A troublesome liquid oxygen valve on the Space Launch System’s first flight-rated core stage will keep NASA from performing a second test-firing of the rocket’s four main engines this week.

A Lockheed Martin Atlas 2AS rocket lifts off from Launch Complex 36B at Cape Canaveral on May 19, 2004, carrying the AMC-11 high-definition TV broadcasting satellite. It was the penultimate mission for the Atlas 2AS, which was fitted with four strap-on solid rocket boosters.