Question: At which airport does the low-cost airline, a subsidiary of KLM founded by John Nicolaas Block, have its main base?
Sentence (from "Transavia"): Transavia, legally incorporated as "Transavia Airlines C.V." and formerly branded as "transavia.com", is a Dutch low-cost airline and a wholly owned subsidiary of KLM and therefore part of the Air France-KLM group.
Relevant evidence: Yes