There's been a good deal of talk on the Internet recently about an AP news story that reported on how the FBI owns about a hundred airplanes that are being used for surveillance missions over the US. It's an interesting story to me because many of the details were figured out by regular people using publicly available data. The Washington Post reported in May that during the Baltimore riots, people noticed two Cessnas were flying circles around the city both day and night. People posted pictures of the planes and then used the tail fins on sites like FR24 to obtain the planes' flight histories and registration information. While working through the details, people realized others had spotted the planes circling elsewhere (see this Reddit thread).
Guessing that these planes were being used by law enforcement, people deduced that the company the planes were registered to was a contractor for the government. They started monitoring that company's planes, and then noticed similarities with other companies that used the same airport in Virginia. They theorized that the companies were all contractors and assembled a list of 84 (now 115) planes that are likely used for government surveillance. Sites like Enigma Blog list out all the planes and tell you how you can use FlightRadar24 to track them.
FBI Flights in My FR24 Data
I extracted the ICAO numbers from Enigma Blog and started going through the data I scraped from FR24 last year to see where the planes went. While my data is too infrequent (6min sampling rate) to see well-defined circling I do have continuous data for most of the year. Using bash and grep I pulled out all of the flights that matched the posted ICAO numbers. I then wrote some scripts to do day-by-day plots with mapnik, so you can see how the flights evolved over the year.
The above plot shows the history. Most of the activity starts in the north east (DC, Baltimore, and New York) and Chicago. Other splotches show up in Texas (Dallas and Houston), Denver, and Southern California (LA and San Diego). By the end of the year, there's also a good bit of work in Northern California (Mostly San Francisco, but also Sacramento?), Seattle, Tuscon, and Miami.
Active Days Per Plane
Looking more closely at the data, 66 of the reported planes flew sometime during last year. Below is a plot that counts up the number of days each plane appeared in the data I captured. The top three planes were A36622, A4105, and A6D306.
Active Planes Per Day
Another way to look at the data is to see how many planes were active on each day in the dataset.
Day of the Week
The planes-per-day plot was jagged, which seemed to suggest some regular patterns to when the planes were being used. I recounted the data into days of the week bins and found that flights were much less likely to happen on the weekend.