I have no idea how the Secret Service in particular is doing, but I would kind of expect that any actual anti-aircraft missiles would be owned and operated by s

I have no idea how the Secret Service in particular is doing, but I would kind of expect that any actual anti-aircraft missiles would be owned and operated by some unit of the Army or National Guard or something. They own all of the actual missiles, and repair and maintenance people and gear, and probably training for how to operate it and how to try not to fuck up when you have 15 seconds to determine if an incoming aircraft is hostile and needs to have missiles fired at it. Also the way they were caught with their pants down on 9/11 kind of suggests that there was no actual military level ordinance readily available around DC at the time. Maybe there is now, but I heard at the time they scrambled some fighter jets with no weapons because there wasn't time to get the weapons out of wherever they were stored and load them up.