*The term is half mast and not half mass
*Half mast is the term describing flying a flag below the summit of the flagpole (mast). This is done in many countries as a symbol of respect and mourning.
*Only flags on ships are flown at half mast, on land they are at half staff (interesting tid bit)
*The US code establishes when they flag should be flown at half staff. See website http://halfstaff.org/ for the whens and whys.
*On Memorial Day the flag should be displayed at half-staff until noon only, then raised to the top of the staff
*By order of the President, the flag shall be flown at half-staff upon the death of principal figures of the United States Government and the Governor of a State, territory, or possession, as a mark of respect to their memory
*The flag shall be flown at half-staff 30 days from the death of the President or a former President
*10 days from the day of death of the Vice President, the Chief Justice or a retired Chief Justice of the United States, or the Speaker of the House of Representatives
*Federal law requires the flag be flown at half-staff on Peace Officers Memorial Day (May 15), unless that day is also Armed Forces Day
*New legislation was signed into effect on June 29, 2007, by President Bush, requiring any federal facility within a region, which proclaims half-staff to honor a member of the U.S. Armed Forces who died during active duty.
* The United States of America is not the only country to observe this tradition. Other countries include; the UK, Zimbabwe, Saudi Arabia, Canada, Russia, New Zealand and Israel, just to name a few.