In general, when booking your flight to Brasilia, February is the cheapest month on average.
In general, most flyers find the cheapest time to book a flight to Brasilia is about 60 days prior.
From most locations, the cheapest flights to Brasilia are found on a Thursday. Booking a Saturday departure is usually the most expensive.
Generally, when visiting Brasilia, midday flights represent the best value. morning flights are likely to have higher prices.