The first crash involved a MH-60R Sea Hawk helicopter, which "went down in the waters of the South China Sea while conducting routine operations from the aircraft carrier USS Nimitz," according to a statement from the US Navy's Pacific Fleet.

All three crew members aboard the helicopter were recovered by search and rescue teams, the statement said.

A half-hour later, according to the Navy, a Boeing F/A-18F Super Hornet fighter jet crashed into the South China Sea, also "while conducting routine operations" from the USS Nimitz.

The Navy's statement said both crew members aboard ejected themselves from the vessel and were safely recovered.

"All personnel involved are safe and in stable condition," the US Navy said. "The cause of both incidents is currently under investigation."

The crashes come as US President Donald Trump is in the region, on his first visit to Asia of his second term, and as Defense Secretary Pete Hegseth prepares to also begin a multi-country Asian tour.

Earlier this year, two US warplanes fell off the US Navy's Harry S. Truman aircraft carrier while operating in the Middle East.