Just before 6:40 p.m. Wednesday night the U.S. Capitol Police issued an alert ordering the immediate evacuation of the U.S. Capitol building, the Capitol visitor center, six Senate and House office buildings, all three buildings of the Library of Congress, and the U.S. Botanic Garden. People inside the House office buildings, the Library of Congress, and the Botanic Garden were ordered to proceed south toward local parks; people in the Senate office buildings or the Senate side of the Capitol were ordered to proceed north, to something ominously described only as the "Aircraft Intrusion Assembly Area." The reason for the evacuation: The Capitol Police were "tracking an aircraft" that they'd determined posed "a probable threat to the Capitol Complex."
Normally this kind of thing would be no laughing matter, but today you are forced to chuckle upon learning that the cause of this dread-soaked evacuation of the literal legislative branch of the federal government was a big dumb patriotic pregame stunt at a baseball game between the Washington Nationals and the Arizona Diamondbacks. It seems that Wednesday was Military Appreciation Night at Nationals Park, the first of four calendar events the team has designated as part of a "Patriotic Series." To celebrate this event, the Nationals scheduled a display by the United States Army Parachute Team, nicknamed the Golden Knights, who were expected to leap from a Twin Otter Series airplane and skydive down into the stadium, located just over a mile from the National Mall. Naturally, this would require flying the airplane in the skies over the stadium, one of the most heavily restricted columns of air anywhere on the planet.
Apparently this plan had not been communicated to the Capitol Police. Despite being coordinated by the United States Army, and despite the plane taking off from Andrews Air Force Base, and despite its pilot being in constant contact with air traffic control at Reagan National Airport, the first that anyone in charge of security at the United States Capitol heard of this flight was when the twin-engine plane started circling ominously at the very edge of the prohibited airspace over the National Mall, at which time "multiple federal agencies began scrambling officials" on the belief that the plane was a "probable threat" to attack the United States Capitol Building. The evacuation order was given, and a bunch of extremely frightened people started racing for safety. It was approximately 10 minutes later that the various parties involved figured out the mixup and the evacuation order was lifted.
According to the Federal Aviation Administration, there are two layers of restricted airspace around Washington D.C.: There is the Special Flight Rules Area (SFRA), which is "roughly a circular area with a 30 nautical mile radius" around the city; and there is a Flight Restricted Zone (FRZ), which "extends approximately 15 nautical miles" around Reagan National Airport. To enter the SFRA, a flight needs "advance clearance from the FAA," needs to have its transponder up and running, needs to have an FAA-assigned tracking number, and "must be in direct contact with air traffic control." To enter the FRZ (which has been in effect since Sept. 11, 2001), flights that are not scheduled commercial flights into and out of Reagan National must be granted permission by the Transportation Security Administration or a waiver by the FAA.
What I have learned from looking all this up this morning—and probably working my way onto several FBI watchlists in the doing—is that there is nothing in the regulations about the pilot calling up the Capitol Police before liftoff. It would appear that responsibility for making the USCP aware of things like this falls to the FAA itself. An unnamed "law enforcement official" told WTOP News that "the FAA did not provide the required notification to the Capitol Police that a plane would be circling overhead," and Wednesday night House Speaker Nancy Pelosi ripped the FAA a new one over the extraordinarily boneheaded lapse in communication:
The FAA issued a statement assuring the public that it "takes its role in protecting the national airspace seriously and will conduct a thorough and expeditious review of the events" of Wednesday evening. A spokeswoman for U.S. Army Recruiting Command, which ESPN says "was behind" the Golden Knights stunt, said in a statement that they are "reviewing all aspects of the event to ensure all procedures were followed appropriately." Shortly after the mixup was discovered Wednesday night and the all-clear was finally given, six Golden Knights skydivers successfully dropped into a sparsely occupied Nationals Park, where scattered fans met them with polite applause and then settled in for the most dispiriting Nationals game of the season, an 11–2 loss to the worst offensive team in baseball.
Since you are definitely thinking about it, ESPN reported that the "several surface-to-air missile sites" responsible for guarding the nation's capital "did not appear" to have been scrambled. Assuming this is true and they were not, we can now rest assured that the United States military did not almost fire missiles at a United States military-owned airplane carrying six United States military stunt skydivers, guided by a United States military pilot, after taking off from a United States military base, for flying in a circle over the capital of the United States. Everything's fine!