It sounded like a story ripped from a narco thriller: One of the biggest drug lords in Mexico was lured onto an airplane, flown across the border and presented to American federal agents by the son of his former partner in crime.

As improbable as it may seem, that is exactly what appears to have happened on Thursday evening, when a Beechcraft King Air turboprop landed at a small municipal airport outside El Paso, and off stepped one of the most wanted men in Mexico: Ismael Zambada García, a founder of the notorious Sinaloa drug cartel.

Mr. Zambada García, known as El Mayo, had for decades evaded capture by both Mexican and American officials, living a life of luxurious simplicity in the mountains of Sinaloa — despite the $15 million U.S. bounty on his head.

But in the end, U.S. officials said, he was betrayed by an unlikely foe: a son of his closest criminal ally, Joaquín Guzmán Loera, the infamous drug lord known as El Chapo, who is now serving a life sentence in an American federal prison.

El Chapo’s son, Joaquín Guzmán López, tricked Mr. Zambada García into boarding the plane, the U.S. officials said, telling him they were going to look at real estate in northern Mexico. The older man had no idea that he was actually en route to Texas, where he would be delivered into the hands of American agents who had long been on his tail.

The dramatic cross-border flight came after years of quiet contact between Mr. Guzmán López and a small team of U.S. law enforcement officers in the F.B.I. and Homeland Security Department who had doggedly been chasing him, his three brothers and Mr. Zambada García in the wake of Mr. Guzmán Loera’s landmark conviction on drug conspiracy charges five years ago.