LAS VEGAS (AP) -- American Pacific Corp., which makes specialty chemicals, explosives and rocket propulsion systems, said Thursday Chairman and CEO John Gibson will retire on Dec. 31 after 12 years of service.

Gibson will be succeeded by Joseph Carleone, who currently serves as president and chief operating officer. Gibson will remain in his role as a non-executive chairman. He joined AMPAC in 1997, after a 28-year career at U.S. Steel.

Under the new leadership structure, Carleone will no longer serve as COO.

The company said succession planning began several years ago to ensure a smooth transition.

Carleone joined AMPAC in October 2006 as president and COO. He was previously senior vice president and chief product officer at Irvine Sensors Corp. He also served as president of Aeorjet Fine Chemicals LLC when AMPAC acquired the business from GenCorp Inc. in November 2005.

Shares fell 15 cents to close at $8.09.