What do the residents begin seeing in the sky in November and what are they doing?

Low-flying planes begin to appear this month that both frighten and excite them. A large four-engine transport flies over at one thousand feet and Sam believes it collects radiation samples. Another transport circles Fort Repose the next week and drops leaflets from its belly. The leaflets announce not to be alarmed or interfere with the United States Air Force conducting atmospheric surveys preliminary to bringing relief to the Contaminated Zones.