The third Friday in September is recognized as POW/MIA Day. The following is from Naval History and Heritage Command, Communication and Outreach Division
The POW/MIA flag, made official by Congress in 1990, may be flown six days a year, smaller and always below the United States flag: Armed Forces Day (third Saturday in May); Memorial Day (last Monday in May); Flag Day (June 14); Independence Day (July 4); National POW/MIA Recognition Day (third Friday in September), and Veterans’ Day (Nov. 11).The day of recognition was created in the 1998 Defense Authorization Act, stating the annual event “honors prisoners of war and our missing and their families, and highlights the government’s commitment to account for them.”And yet thousands remain unaccounted: World War II has at least 73,000 missing plus those lost at sea; 7,500 from the Korean War, 1,600 from Vietnam, 126 during the clandestine operations of the Cold War years, and two from Desert Storm. Both of those missing are Navy pilots whose planes went down in the Persian Gulf: Lt. Cmdr. Barry T. Cooke, flying an A-6 aircraft on Feb. 2, 1991, followed by Lt. Robert J. Dwyer, in his FA-18 aircraft on Feb. 5, 1991.
If you’ve ever been to a military ball, stepped inside a chow hall, or attended an event at a military veterans association in your local community, you’ve likely noticed the small, round table that is always set but never occupied—the prisoners of war/missing in action (POW/MIA) table.
The tradition of setting a separate table in honor of our prisoners of war and missing comrades has been in place since the end of the Vietnam War. The manner in which this table is decorated is full of special symbols to help us remember our brothers and sisters in arms. Those symbols are spelled out in OPNAVINST 1710.7A.
The POW/MIA table is smaller than the others, symbolizing the frailty of one prisoner alone against his or her oppressors. This table is separate from the others and can be set for one to four place settings to represent each service participating in the event.
The white tablecloth draped over the table represents the purity of their response to our country’s call to arms.
The empty chair depicts an unknown face, representing no specific Soldier, Sailor, Airman, or Marine, but all who are not here with us.
The table itself is round to show that our concern for them is never ending.
The Bible represents faith in a higher power and the pledge to our country, founded as one nation under God.
The black napkin stands for the emptiness these warriors have left in the hearts of their families and friends. A Purple Heart medal can be pinned to the napkin.
The single red rose reminds us of their families and loved ones. The red ribbon represents the love of our country, which inspired them to answer the nation’s call.
The yellow candle and its yellow ribbon symbolize the everlasting hope for a joyous reunion with those yet accounted for.
The slices of lemon on the bread plate remind us of their bitter fate.
The salt upon the bread plate represent the tears of their families.
The wine glass, turned upside down, reminds us that our distinguished comrades cannot be with us to drink a toast or join in the festivities of the evening.

The significance of the POW/MIA table is called to attention during the toast of the evening. This is an important part of many military banquets to remind us that the strength of those who fight for our country often times rests in the traditions that are upheld today.

http://usnhistory.navylive.dodlive.mil/2014/10/06/the-powmia-table-a-place-setting-for-one-a-table-for-all/