January and February are generally the cheapest months to book flights. This is mainly due to the low post-Christmas demand, when most people have finished their vacations and returned to their daily routines.

https://sites.google.com/view/alaska-airlines-mexico/home
https://sites.google.com/view/tap-portugal-es-pt/home
https://sites.google.com/view/qatar-airways-es-es/home