1
general::
At the announced or expected time, as in Her first baby arrived right on schedule. Originally alluding to published railroad timetables, this expression dates from the late 1800s.
American Heritage Idioms
2
general::
Phrase(s): on schedule
at the expected or desired time. • The plane came in right on schedule. • Things have to happen on schedule in a theatrical performance.
McGrawhill's American Idioms And Phrasal Verbs