The KLM API offers similar functionality to Duffel, but will only allow you to access content from KLM.
If you want to access content from other airlines, you would need to integrate with each individual airline's API, a process that is costly and time-consuming
With Duffel, you get access to a network of 300+ of the world's leading airlines with just a single integration.
Duffel was also built with the developer in mind and offers simple, composable APIs, comprehensive documentation, and a robust testing environment. This means an integration takes minutes, not months. Check out our API Documentation here