"A United States Navy aircraft carrying 11 crew and passengers crashed into the ocean southeast of Okinawa," a statement from the Navy said.
Personnel recovery is under way and their condition will be evaluated by USS Ronald Reagan medical staff.
The Japan-based 7th Fleet says in a statement that the search and rescue operation has been launched from the carrier.
It says the ship was operating in the Philippine Sea when the crash occurred at 2:45 p.m. Japan time.
It says the names of the crew and passengers are being withheld pending next of kin notification.
The US miltary has a heavy presence in the western Pacific, with tens of thousands of troops and hundreds of pieces of hardware stationed in Japan and South Korea.
The USS Ronald Reagan last week was one of three American aircraft carriers that held rare joint drills in the region, joined separately by Japanese navy and South Korean warships over the weekend.
The drills come as tensions persist between Washington and North Korea over its missile and nuclear programme.
US military vessels have been involved in a number of accidents in recent months in East Asia.
The USS John S. McCain collided with a tanker off Singapore in August, killing 10 sailors and injuring five others.
Two months earlier in June, the USS Fitzgerald and a cargo ship smashed into each other off Japan, leaving seven sailors dead.
There were also two more, lesser-known incidents. In January USS Antietam ran aground near its base in Japan, and in May, USS Lake Champlain collided with a South Korean fishing vessel.