A flight created in AGOA from a manual schedule cannot be deleted directly by users. If the flight already exists in AGOA, support must remove it. If the flight is more than 48 hours in the future and hasn't been created in AGOA yet, deleting the schedule will prevent it from being created.
So if a schedule is incorrect, the best approach is to delete the whole schedule and recreate it with the correct information. To delete a schedule, go to the Schedules section in the Backoffice and open it from there.