My guess:
We had a top secret nuclear accident in one of our Midwest silos or at a research lab. The drones are in the East where the likely wind path would take the “dirty” air. They are testing at 1000 feet and higher with nuclear sensors to see if the levels ae high enough to issue a public warning.
Someone with a sophisticated air tester could “test” this theory.
The east coast is where there are many nuclear power plants. There are many radiation sensing instruments located at these plants that would p would possibly detect radioactivity greater than the usual background. These power stations would be very responsive to signs increasing radiation. This was how Chernobyl accident was detected by countries before the USSR announced the event.
“see if the levels are high enough to issue a public warning.”
Like: “Residents of the state of Virginia please evacuate?”
Lol.
They would not say a word no matter what they found.
At most they would get additional medical supplies and hospital beds to the state (and hope nobody noticed).
Remember how long it took the Soviet Union to tell the public after Chernobyl? Bureaucratic .gov will always delay until after most of the damage is done. The Biden WH is at least as bureaucratic as the old Soviet Union—and probably even more incompetent.