ON TIME vs IN TIME

          ON TIME You do the action at the planned time. Punctual, not late. (The opposite is LATE).

            We took the plane on time, at 16:30 in the afternoon

IN TIME You do the action before the last moment, with enough time to spare. (The opposite is TOO LATE).

            We went to the airport in time, we could even buy some presents at the duty free

            *IN TIME Eventually, in the future, after time passes.

            Although we have split, we'll be together in time