Regardless of the time of day you decide to fly, the ticket price will remain around the same. Book flights from Belfast City Airport to South America as you normally would.
Yes, there are multiple flights from Belfast City Airport to South America for under £1,400. The cheapest flight booked recently is on American Airlines for just £1,365, but on average you can expect to pay £2,314.
The most popular route from Belfast City Airport to South America is Belfast City - Cartagena Rafael Nunez. You may also consider Belfast City - Barranquilla E Cortissoz or Belfast City - Bogotá El Dorado.