WASHINGTON, Dec. 13, 2007 – Santa’s USO elves will be checking their list twice this weekend to ensure they’re ready to host about 2,000 troops slated to transit through Baltimore-Washington International Thurgood Marshall Airport before catching flights home to their families and loved ones. The elves – actually volunteers from United Service Organizations of Metropolitan Washington – will work through the night Dec. 15 to prepare for a mass holiday exodus to begin at the suburban Maryland airport at 6 the following morning. As some 1,800 soldiers attending advanced individual training at nearby Aberdeen Proving Ground, Md., await their flights,...