My company xmltravelgate.com offers a flight API (search & book) with many direct airlines (low cost and NDC) and 3 GDS already integrated, although you do need

My company xmltravelgate.com offers a flight API (search & book) with many direct airlines (low cost and NDC) and 3 GDS already integrated, although you do need a contract with them... We're releasing a new aggregated flight API and flight cache API (only price & availability, no booking, no contracts) based on GraphQL scheduled for January. Feel free to contact me for more details.