A $25B US counter-drug smuggling operation quietly thrives far south of the border

CORPUS CHRISTI, Texas — Smugglers flying small cocaine-packed airplanes toward the United States from South and Central America might make it to Mexico thinking they went undetected by American forces staked out in international waters trying to interdict them.

But once on the ground in Mexico, from where they hope to smuggle their contraband into the United States, those tiny planes will be greeted by a swarm of Mexican law enforcement. What’s more, they will never know a Department of Homeland Security plane was flying within 100 feet of them,...