When you say that the meeting took place “as scheduled”, what you mean is that the meeting took place as planned. Arrangements had been made, in advance, for the meeting to be held and things went according to plan.
*The Opposition called for a bandh, but we managed to meet the minister as scheduled.
The expression “on schedule” is normally used to refer to time. When a project is completed on schedule, it is completed on time.
*For a change all flights left on schedule.