The locations are significant, with Isabela and Cagayan facing north towards Taiwan, while Palawan is near the disputed Spratly Islands in the South China Sea, where China has built artificial islands equipped with runways and missile systems.
Defence chief Carlito Galvez called the sites "very strategic" and stressed the Philippines had a responsibility to the international community in the South China Sea.
"Their locations are in areas where they are needed," said Jay Batongbacal, a South China Sea expert at the University of the Philippines.
"It also provides us with coverage not only on the West Philippine Sea (South China Sea) but also on the Pacific side," he added.
The United States has committed more than $80 million worth of infrastructure at the five existing sites - the Antonio Bautista Air Base in Palawan, Basa Air Base in Pampanga, Fort Magsaysay in Nueva Ecija, Benito Ebuen Air Base in Cebu and Lumbia Air Base in Mindanao.