When they caught up with the abandoned airplane, they discovered more than 140 pounds of meth and fentanyl.
The agency posted a collection of images on its Twitter page showing the ultralight modified to hold a storage bin filled with the illegal narcotics on either side of the fuselage.
An AMO helicopter crew and Border Patrol agents conducted an exhaustive search of the area, but did not find the presumed pilot.
The agency estimated that the seizure would have a street value of a half million dollars.