Ten US Navy sailors are missing after a US Navy guided-missile destroyer collided with an oil tanker east of Singapore early Monday, the fourth accident in Asian waters involving a US warship in 2017.

The Navy’s 7th Fleet said the USS John S. McCain collided with the merchant vessel Alnic MC while the destroyer was making its way to a port visit in Singapore. The collision was reported at 5:24 am local time, east of the Malacca Strait, one of the world’s most congested shipping routes.

The Navy reported significant hull damage to the McCain, saying there was flooding in berthing compartments as well as machinery and communication rooms.

Pacific naval impact

The collision comes at a time of high tensions in the Pacific.

The McCain is equipped with the Aegis missile defense system, which has been touted as a possible counter to any North Korean missile launch. If it is out of action after Monday’s collision, it would mean at least 3 of 11 Aegis warships based at Yokosuka Naval Base in Japan are unavailable for deployment.

The US Navy fleet has 84 warships equipped with the Aegis missile defense system.

The McCain’s last high-profile mission was earlier this month, when it performed a freedom-of-navigation exercise near a Chinese-claimed island in the South China Sea.

No fuel or oil was seen on the water near the ship after the collision on Monday as it steamed under its own power to Changi Naval Base in Singapore, arriving in the afternoon, the Navy said.

Malaysian officials said their ships and aircraft had joined the search for the missing US sailors.

The search area encompassed 100 nautical square miles, they said, describing sea conditions as rough, with waves up to 1 meter (3.2 feet) high.

In addition to the 10 missing sailors, the Navy said five were injured in the collision. Four of those were flown by a Singapore Navy helicopter to a hospital in Singapore with non-life-threatening injuries, Navy said.

US helicopters and Marine Corps Osprey aircraft from the amphibious assault ship USS America were joining search and rescue efforts along with Singaporean ships and helicopters, the Navy said.

The McCain collision marks the fourth incident involving a US Navy warship in the Pacific this year.

On June 17, the USS Fitzgerald collided with a container ship off the coast of Japan. That collision resulted in the deaths of seven US sailors. The Fitzgerald will be transported to the US for repairs.

On May 9, the guided-missile cruiser USS Lake Champlain was struck by a small fishing boat off the Korean Peninsula.

And in late January, the guided-missile cruiser USS Antietam ran aground while trying to anchor in Tokyo Bay. Authorities at Yokosuka Naval Base said the Antietam remains out of action.

Military experts said the latest incident calls into question the Navy’s training and will likely lead to a serious shake-up among the Navy’s leadership.

“I can almost guarantee you that there will be a tumultuous shake up in the senior leadership of at least the 7th Fleet and maybe the Navy in general,” CNN military analyst Rick Francona said.

“The Navy is not looking good about now, especially when we need those … Aegis-equipped ships for possible ballistic missile defense in a North Korean scenario,” he added.

In a report on the Fitzgerald collision released just last week, the Navy it would review its training and qualification procedures.

“The collision was avoidable and both ships demonstrated poor seamanship. Within Fitzgerald, flawed watch stander teamwork and inadequate leadership contributed to the collision,” a 7th Fleet statement said.

Oil tanker ‘three times bigger’

Carl Schuster, a former director of operations at the US Pacific Command’s Joint Intelligence Center, said the oil tanker would have been at least three times bigger than the USS John S. McCain.

“Oil tankers are huge and it takes miles for them to change course,” he said.

“When you’re going into a congested channel, you’re supposed to be very alert, track ships around you to a very meticulous degree.”

The Malacca Strait, which runs between Indonesia, Malaysia and Singapore, is the world’s second busiest waterway according to the World Economic Forum. The collision took place in waters to the east of the Malacca Strait, US authorities said.

At a press conference Monday afternoon, Malaysian authorities said both ships were heading toward Singapore from the South China Sea when the collision occurred. They described the area as very busy, with some 80,000 ships passing through it every year.

Both ships should have reported in to what the Malaysian authorities called a maritime “traffic separation scheme,” essentially air traffic control for ships.

Francona said no matter what the tanker did, the faster, more-nimble US destroyer should have been able to avoid a collision.

“How does a state-of-the-art Navy destroyer equipped with multiple radar systems and communications gear with a full bridge watch not see, detect and evade a 30,000 ton slow-moving (10 knots) behemoth?” Francona asked.

Search and rescue

A US Navy official told CNN the McCain had experienced a loss of steering before the collision, but that steering had been regained.

Merchant marine websites describe the Alnic MC as a 30,000-ton, 600-foot-long oil tanker flying a Liberian flag.

The Maritime and Port Authority of Singapore said the Alnic sustained damage to a tank at its bow, about seven meters (23 feet) above the waterline. No one was injured on the tanker, it said, and no oil spill was reported.

The McCain is named for the father and grandfather of US Sen. John McCain. Both of McCain’s relatives were US Navy admirals. The senator was a captain in the US Navy.

The vessel is 505 feet long and displaces about 9,000 tons.