You are going to have to elaborate on "they even tell you what they are doing"

But in many circumstances...contrails are exactly like clouds. They have a density...and may show up on radar...just like clouds. In some instances the water vapor may even become ice crystals. In addition....aircraft have "lanes" that ATF will typically funnel the traffic through. So its not unusual to have 20-30 aircraft go over the same area in an hour. If the conditions are right....the airplane traffic in a concentrated area can actually manufacture cloud cover that is quite substantial. Many times this will show up on radar. Happens EVERYDAY somewhere in which the conditions are right.