According to Kayak itself, the best time for domestic is 3-7 weeks out, and for international destinations it varies by continent: http://www.kayak.com/news/KAY

According to Kayak itself, the best time for domestic is 3-7 weeks out, and for international destinations it varies by continent: http://www.kayak.com/news/KAYAK-Travel-Guide-2014.bd.html http://www.kayak.com/news/KAYAK-Travel-Guide-2014.bd.html