I asked an ex-military friend who used to work in the Key West area, about the weakness of our Southern air-defense, and here is what he told me:

When the military got dragged into the War-On-Drugs, it came under much pressure from Washington to find a reliable method to determine which aircraft are carrying drugs. As a result, all of the human radar operators have been replaced by specially-trained, drug-sniffing dogs. Whenever the dog sees a new blip on the radar screen, he sniffs at it, and if he detects drugs, he barks, which alerts the supervisor (a human), who sounds the alarm.