The brief flag mix-up comes as the royal couple prepares for a four-day state visit beginning April 27, timed to America's 250th anniversary. The itinerary includes a state dinner, a private tea, a garden party and a ceremonial military review. The King is also set to address a joint meeting of Congress, only the second British monarch to do so. Later stops include New York — with a visit to One World Trade Center and a reception for The King's Trust — and events in Virginia, including a national-park “block party.” The trip unfolds amid political tensions between London and Washington and follows a security incident at the White House Correspondents' Dinner two days earlier.