1
general::
Everything is ready for proceeding, as in They've rented a hall and lined up the speakers, so it's all systems go for the rally. Originating in the late 1960s with reference to launching space missiles and vehicles, this expression has been transferred to general use.
American Heritage Idioms
2
general::
Phrase(s): All systems (are) go.
Cliché Everything is ready. (Originally said when preparing to launch a rocket.) • The rocket is ready to blast off—all systems are go. • Tom: Are you guys ready to start playing? Bill: Sure, Tom, all systems go.
McGrawhill's American Idioms And Phrasal Verbs