https://en.wikipedia.org/wiki/Half-mast
In the United States, the usual government term for non-nautical use is "half-staff." While the term "half-mast" is commonly used in place of half-staff, U.S. law and post-WW-I military tradition indicate that "half-mast" is reserved to usage aboard a ship, where flags are typically flown from masts, and at naval ships ashore.[67][68]
In the United States, the President can issue an executive order for the flag of the United States to be flown at half-staff upon the death of principal figures of the United States government and others, as a mark of respect to their memory. When such an order is issued, all government buildings, offices, public schools, and military bases are to fly their flags at half-staff. Under federal law (4 U.S.C. § 7(f)), the flags of states, cities, localities, and pennants of societies, shall never be placed above the flag of the United States; thus, all other flags also fly at half-staff when the U.S. flag has been ordered to fly at half-staff. There is no penalty for failure to comply with the above law as to enforce such a penalty would violate the First Amendment.[citation needed]
Governors of U.S. states and territories are authorized by federal law to order all U.S. and state flags in their jurisdiction flown at half-staff as a mark of respect for a former or current state official who has died, or for a member of the armed forces who has died in active duty. The governor's authority to issue the order is more restricted than the president's, and does not include discretion to issue the order for state residents who do not meet the criteria stated.[citation needed] Since a governor's executive order affects only his or her state, not the entire country, these orders are distinguished from presidential proclamations.
Under 4 U.S.C. § 7(m) and established traditions by Presidential proclamations, the flag of the United States is to be flown at half-staff on rare occasions, in the following circumstances:[69]
For thirty days (or a month) after the death of a current, former president, or president-elect.
For ten days after the death of a current vice president, current or retired chief justice, or current Speaker of the House of Representatives.
From the day of death until interment of an Associate Justice of the Supreme Court, a secretary of an executive or military department, a former vice president or a former Speaker of the House, the President Pro Tempore of the Senate,[70] or the governor of a state, territory, or possession.
On the day of death and the day after[71] for a Member of Congress.
On Memorial Day until noon.
Upon presidential proclamation, usually after the death of other notable figures or tragic events.[72]
Federal law includes a Congressional request that the flag be flown at half-staff on Peace Officers Memorial Day (May 15), unless that day is also Armed Forces Day. Presidential proclamations also call for the flag to be flown at half-staff on Pearl Harbor Remembrance Day (December 7),[73]
On October 16, 2001, President George W. Bush approved legislation requiring the United States flag to be lowered to half-staff on all Federal buildings to memorialize fallen firefighters. Pub.L. 107–51 (text) (pdf) requires this action to occur annually in conjunction with observance of the National Fallen Firefighters Memorial Service.[74] The date of the National Fallen Firefighters Memorial Service is traditionally the first Sunday in October. It is held at the National Fallen Firefighters Memorial in Emmitsburg, Maryland.[75]
4 U.S.C. § 7(m) was modified with new legislation signed into effect on June 29, 2007, by President George W. Bush, requiring any federal facility within a region, which proclaims half-staff to honor a member of the U.S. Armed Forces who died on active duty, to follow the half-staff proclamation.[76]