Conflict of interest: M. Hagner has nothing to disclose. Conflict of interest: D.L. Frey has nothing to disclose. Conflict of interest: M. Guerra has nothing to disclose. Conflict of interest: A.S. Dittrich reports grants from German Cystic Fibrosis Association Mukoviszidose e. V. (grant number 1605), during the conduct of the study. Conflict of interest: V.S. Halls has nothing to disclose. Conflict of interest: S. Wege has nothing to disclose. Conflict of interest: F.J.F. Herth reports personal fees from Uptake, BTG, Olympus, Pulmonx and Roche, outside the submitted work. Conflict of interest: C. Schultz reports grants from Bundesministerium fuer Bildung und Forschung (Deutsches Zentrum fuer Lungenforschung), during the conduct of the study. Conflict of interest: M.A. Mall reports grants from German Federal Ministry of Education and Research (grant 82DZL004A1), German Research Foundation (grant SFB-TR84TP B08) and Einstein Foundation Berlin (grant EP-2017-393), during the conduct of the study; personal fees for consultancy and lectures from Bayer, personal fees for advisory board work, consultancy and lectures from Boehringer Ingelheim and Vertex Pharmaceuticals, personal fees for advisory board work and consultancy from Polyphor, Arrowhead Pharmaceuticals, ProQR Therapeutics, Spyryx Biosciences, Santhera and Enterprise Therapeutics, personal fees for consultancy from Galapagos and Sterna Biologicals, personal fees for lectures from Celtaxys, outside the submitted work; and is listed on a patent on the Scnn1b-transgenic mouse with royalties paid.