4Y1A International Civil Aviation ICAO. From DXNews.com30/11/2021 by PY3TX4U1A Team will be active as 4Y1A from Vienna, Austria, for International Civil Aviation Day, 7 – 11 December 2021. Previous articleA22LL Botswana. From DXNews.comNext article JX/LB5SH Jan Mayen Island. From DXNews.com