All this week, the Department of Defense conducted tests of how well various radar systems could detect small aircraft flying low over the Washington, DC area. The two test aircraft were a Cessna 206 and a Twin Otter. The Cessna is a small (36 foot wingspan, 28 feet long) aircraft with a top speed of 270 kilometers an hour. The Cessna can easily carry about half a ton of explosives. The Twin Otter is a larger, twin engine, propeller driven aircraft. With a 65 foot wingspan, and 52 feet long, it can carry at least a ton of explosives. These two aircraft were flying low over areas that are normally off-limits at that altitude. Various ground and air based radars were used to see exactly how well these two potential terrorist aircraft can be tracked. How well these aircraft types show up on radar, when flying low over Washington, had never been an issue before. But now it is, and the Department of Defense wants to know how easy, or difficult, it would be trying to track a suicidal pilot flying an aircraft, loaded with explosives, with homicidal intent. The results of these tests will, obviously, be kept secret. No point in giving terrorists a map showing where small aircraft are hard to track, and shoot down.