SWISS (the Swiss international airline) offers an affiliate programme where you can integrate links or ads on your website and earn commission on flight bookings made via those links. Partners get benefits like:
~1.5 % commission on the flight fare
14-day cookie tracking
Advertising materials and marketing support
Short confirmation cycles and reputable global brand integration
They manage this through affiliate networks such as Awin (Switzerland) and CJ in other regions, making it relatively easy to join via those platforms