Oldie but goodie
http://www.whatdoesitmean.com/index2576.htm
FLYING THE FLAG AT HALF-STAFF: The pertinent section of the Flag Code says, "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 possesion, as a mark of respect to their memory. In the event of the death of other officials or foreign dignitaries, the flag is to be displayed at half-staff according to Presidential orders, or in accordance with recognized customs or practices not inconsistent with law.
There aren't nearly enough tits in these breads for Q to show up.