KLM banned former pilot Willem Felderhof, in a non-disclosure clause, from ever discussing the presence of toxic fumes on board airplanes. The pilot suffers from headaches, disrupted balance and delayed response times. His neurologist is convinced that Felderhof’s symptoms are caused by what’s known as ‘aerotoxic syndrome’, because of which he is no longer able to fly. When his contract was terminated, KLM drew up detailed non-disclosure clauses. Felderhof is prohibited from offering “his opinion, his views and the facts regarding the air quality in KLM airliners in connection with his health condition, employment conditions and ‘aerotoxic syndrome’.” Should Felderhof breach the clause, the penalty compels him to refund his severance pay of € 300.000 to KLM.