He assisted his father, helping draft correspondence and articles related to epistemology and physics.[3] In September 1943, word reached his family that the Nazis considered them to be Jewish, because Aage's grandmother, Ellen Adler Bohr, had been Jewish, and that they therefore were in danger of being arrested. The Danish resistance helped the family escape by sea to Sweden.[9] Bohr arrived there in October 1943, and then flew to Britain on a de Havilland Mosquito operated by British Overseas Airways Corporation. The Mosquitoes were unarmed high-speed bomber aircraft that had been converted to carry small, valuable cargoes or important passengers.