 In 1990, the last combat aircraft, a squadron of F-4 fighter-bombers, were transferred to Alaska.On 10 June 1991, two days before Mount Pinatubo began the summer-long series of eruptions, Clark Air Base was completely evacuated of all but mission essential personnel.In July 1991, the U.S. and Philippine government agreed to a new treaty regarding the lease of the Subic Bay Naval Base, Clark, and several other U.S. military installations in the Philippines.