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

The last Delta 4-Medium rocket lifted off from Cape Canaveral Thursday with a GPS navigation satellite for the U.S. Air Force.

Early Friday morning, the 8-million-pound mobile service tower was retracted from around the Atlas 5 rocket, revealing the 189-foot-tall vehicle for liftoff from Vandenberg Air Force Base, California, carrying the commercial WorldView 4 Earth-imaging satellite.

A United Launch Alliance Delta 4-Heavy rocket blasted off from Cape Canaveral at 1:51 p.m. EDT (1751 GMT) today to haul a classified satellite into space for the U.S. National Reconnaissance Office. Follow the mission in our live journal.