berlin decision u.s. president donald trump withdraw paris climate agreement would send good signal separate deal agree last year seek curb aviation emissions global airlines body iata say thursday aviation part paris accord fight climate change industry last year agree deal combat aviation pollution also know carbon offset reduction scheme international aviation corsia decision withdraw paris agreement u.s. send good signal even u.s. could remain corsia withdraw paris agreement decide two completely separate iata director general alexandre de juniac say thursday u.s. withdrawal paris deal good sign aviation accord iata