Regardless of the time of day you decide to fly, the ticket price will remain around the same. Book flights from Belfast to Ottawa as you normally would.
For a flight from Belfast to Ottawa, you will be flying into Ottawa. Ottawa (YOW) is just 6.6 mi from the center of the city. Ottawa is the only Ottawa airport and it handles 0 inbound flights from Belfast per day. 0 airlines have flights to Ottawa from Belfast on a regular basis.