Monitor US Government/Military Aircraft Activity
This website is very interesting and handy. Not all government/military planes are visible for obvious reasons. However, in the image below, you can see what looks like a conga line of large military transport planes (C-30, C-130, C-17) going into and out of the DC area
When you go to the website for the first time you will see a TON of air traffic. To filter the commercial air traffic out, click the “U” in the upper right corner of the map (see image below). This will leave you with a view of the government and military aircraft in the air at the current moment. Again, likely not all but what we can see.