I have done that many times when they were actively spraying gridlines over my area and "Surprise" there was absolutely NO scheduled or active flight plans listed whatsoever! Where I live, there is a "No Fly Zone" during certain hours of every day for commercial air travel, so that makes it far easier to find out what is flying up there...According to the FAA, nothing is flying. So, I guess my eyes are LYIN'?   The planes I have seen are unmarked and are at least as big as 747's (Maybe bigger?) There are NO numbers on them and no identifying marks of any kind. I have used both binoculars AND a high powered telescope and seen NOTHING on the planes.