<Li> On disasters causing more than 100 killed--across all the country upon Presidential proclamation . </Li> <Li> On disasters causing more than 10 killed--in a suffering region upon proclamation of a Governor . </Li> <Li> On other tragic occasions . For example, national mourning was proclaimed and all the state flags were flown at half - mast after the Polish President's plane crash near Smolensk, Russia despite the number of casualties being slightly fewer than 100 . After the Assassination of Andrei Karlov, the Russian ambassador in Turkey, in December 2016, the Russian flag was flown in half - mast on all Russian embassies in the world . </Li> <P> All the regional flags and the departmental ensigns are flown at half - mast on national or regional mourning days as well as the national flag . Firms and non-governmental organizations, embassies and representatives of international organizations often join the mourning . National or regional mourning usually lasts for one day . </P>

When is american flag flown at half mast