They quickly learned that the US radar systems installed have trouble distinguishing low flying, slow going ultralights from ground vehicular traffic.
The profit on one haul dwarfs the cost of the ultralight which can be abandoned. Crossing in areas where windmills may be present is even easier I’d expect.
Where the drones when you need them?
Sending a Predator missile from a drone would pretty much swat that mosquito out of the sky. That happens a couple dozen times, it would be hard to find prospective pilots to run this particular airlift.
As long as the profit margin is high, people will find a way to get this stuff in. If we spend another fifty billion and find a way to stop all these ultralights, they’ll just start using something else, like catapults.
We we see them all the time. We just aren’t allowed to do anything about it.
Ultralights aren't all the expensive, are they? I wonder what the max payload is.