An aircraft carrying 11 crew and passengers crashed into the Pacific Ocean on Wednesday while on the way to the aircraft carrier USS Ronald Reagan, the Navy said.
The Japan-based 7th Fleet said in a statement that the search and rescue operation was launched from the carrier.
"Personnel recovery is underway and their condition will be evaluated by USS Ronald Reagan medical staff," the statement said.
It said the ship was operating in the Philippine Sea, which is east of the Philippines, when the crash occurred at 2:45 p.m. Japan time. The names of the crew and passengers are being withheld pending next of kin notification.
The cause of the crash was not immediately clear, the Navy said.
The 7th Fleet has had two fatal accidents in Asian waters this year, leaving 17 sailors dead and prompting the removal of eight top Navy officers from their posts, including the 7th Fleet commander.
The USS John S. McCain and an oil tanker collided near Singapore in August, leaving 10 U.S. sailors dead. Seven sailors died in June when the USS Fitzgerald and a container ship collided off Japan.
The Navy has concluded that the collisions were avoidable and resulted from widespread failures by the crews and commanders, who didn't quickly recognize and respond to unfolding emergencies. A Navy report recommended numerous changes to address the problems, ranging from improved training to increasing sleep and stress management for sailors.