Last Updated Nov 23, 2017 1:12 AM EST
Three people were still missing Wednesday night, after a. Eight others were rescued.
According to initial reports, the plane suffered a rare twin-engine failure 575 miles south of Okinawa, Japan, near the end of a routine run out to the carrier Ronald Reagan.
The fact that eight aboard survived suggests the pilot was able to make a controlled landing in the water.
The plane was near the end of its flight to the carrier, so helicopters were on the scene a half hour after it went down. The search for the three missing continued into the night.
The U.S. Navy said the families of the three service members missing had been notified of their "duty status whereabouts unknown (DUSTWUN)" status as of early Thursday. Their names were being withheld for up to 72 hours, in line with Navy policy.
The plane is called a C-2 Greyhound, but is widely known as a COD (carrier onboard delivery). For more than 50 years, the Navy has used it to deliver people and parts to aircraft carriers at sea.
Last week, CBS News correspondent Ben Tracy was a passenger on a similar flight out to the Reagan, and all passengers were required to wear life vests.
The Reagan recently completed three rare carrier operations intended as a show of force toward North Korea, and was midway through an exercise with the Japanese Navy when the accident occurred.
The COD has a good safety record. The last mishap was five years ago, and there were no fatalities.
But the Navy's 7th Fleet, which operates in the western Pacific, has an atrocious safety record so far this year. Collisions involving the destroyers Fitzgerald and McCain caused the deaths of 17 sailors. And in each case, the ship's crew was at fault.
The cause of this accident is under investigation. But earlier this month, the Navy said the high tempo of operations in the Pacific has led to reduced safety margins.