TIJUANA, Mexico — A few of the cartels’ drones have crashed. How many more have made it across the border is a matter of guesswork, like so much in this city so close to the United States.

One drone that we know of soared over the streets where tourists are invited to take pictures with zonkeys (local burros painted to look like zebras) and vendors sell statues of the Virgin Mary alongside Bart Simpson T-shirts. There is always something of the circus here: illusion, chicanery, and imagination in the service of survival.

All seemed to be going well for that inexpensive Chinese drone, at first. It’s normally outfitted with a camera, and was designed to carry a payload of up to 15 pounds. But then it collapsed under the weight of six and a half pounds of methamphetamine and plunked down in a supermarket parking lot about 10 blocks short of the existing wall. One was reminded of those old films of the first flapping, failing flying machines at the beginning of the last century.