The Air Force sent two nuclear-capable bombers over the South China Sea on Wednesday in a show of force challenging China's expansive maritime claims.
"Two B-52H Stratofortress bombers took off from Andersen Air Force Base, Guam, and conducted routine training in the vicinity of the South China Sea March 13, before returning to base," Air Force Capt. Victoria Hight, a Pacific Air Forces spokeswoman, said in a statement.
Hight said U.S. aircraft conduct routine operations in the South China Sea to support "allies, partners, and a free and open Indo-Pacific."
"U.S. Pacific Air Forces bombers have flown from Guam for more than a decade as part of U.S. Indo-Pacific Command’s continuous bomber presence operations," she added.
A military official said no Chinese fighters were sent to intercept the bombers. However, a regional air controller radioed the bombers to leave the area and asserted they were not authorized.
An air crew member on the bomber responded by telling the controller, "We’re U.S. Air Force aircraft operating in international airspace," the official said.
No other details of the mission were released.
It was the second flight of B-52s in the sea this month. Two other bombers, also from Guam, conducted a bomber presence mission on March 4. Prior to that overflight, bombers were over the sea in November.
The bomber mission was first disclosed on Twitter Tuesday night by military flight monitor @AircraftSpots around 11:00 p.m.
The tweet stated that the bombers had just entered the South China Sea and included a map based on the tracking signals. The aircraft were identified by their air control call signs as "Roost 01 and Roost 02." The bombers were supported with two KC-135 refueling tankers, the tweet stated.
The tracking map showed the bombers entered the sea through the Luzon Strait, the waterway between Taiwan in the north and the Philippine island of Luzon in the south.
The likely flight path showed the bombers heading over the disputed Paracel islands where China has deployed some of its advanced air defense missiles.
China is claiming sovereignty over 90 percent of the South China Sea and over the past decade has built up some 3,200 acres of new islands in the Paracels and further south in the Spratlys.
Despite a promise from Chinese President Xi Jinping in 2015 not to militarize the islands, China has done just that.
Beginning in April 2018, advanced anti-ship and air defense missiles have been spotted at several locations in the sea.
B-52s are capable of carrying both conventional and nuclear missiles. When nuclear-armed, the bombes carry up to 20 AGM-69 short-range attack missiles.
Recent conventional armament upgrades have included the capability of carrying Joint Direct Attack Munition and Wind Corrected Munitions Dispenser guided bombs, the AGM-154 glide bomb and the AGM-158 joint air-to-surface standoff missile.
The bomber flights are part of increased overflight and freedom of navigation operations designed to assure the South China Sea remains international air space and waters.
Adm. Philip Davidson, commander of the Indo-Pacific Command, told the Senate Armed Services Committee last month that the freedom of navigation operations have been widened to include regional and international allies and partners.
"These operations are critically important, not just for the United States, and they're not about two destroyers passing safely in this region," Davidson said.
"This is about the free flow of communications. That's oil. That's trade. That's economic means. It means the cyber connectivities on the cables that travel under the South China Sea, which are deep and profound coming out of Singapore, and it includes the free passage of citizens between all the great nations of the world."
China's missiles on the disputed island threaten both civilian and military aircraft, Davidson said.
"If you're taking a flight from Singapore to San Francisco, from Sydney to Seoul, from Manila to Tokyo, you are flying over the South China Sea," he said.
"And each time that happens, there is somebody with a surface-to-air missile and a Chinese soldier evaluating whether that traffic can go on a day-to-day basis. I think it's quite hazardous to the global security, and I think it's quite pernicious that China would take such action."
Davidson said China recently sought to dictate to regional states when and where they were permitted to sail in the South China Sea.
Davidson added that "helping them protect the international freedoms of the seas and airspace that have been long established in maritime law that the United States and others have fought for over the centuries is quite important."
The four-star admiral was asked by one senator during the hearing if the command has contingency plans for responding to a shootout or other incident in the sea.
"Sir, to your last point about contingency plans, I'd rather hold that for the closed hearing if I could."
In September, the USS Decatur, a guided missile destroyer, conducted a freedom of navigation cruise near the Spratlys.
The warship was confronted by a Chinese Luyang-class guided missile destroyer that came within 45 yards of the Decatur, nearly causing a collision.
The most recent warship passage took place Feb. 16 when the guided missile destroyers USS Spruance and the USS Preble sailed near the Spratlys.
And on Jan. 7 the USS McCampbell, conducted a similar freedom of navigation operations near the Paracels.
Further north, two other Navy ships, the guided missile destroyer USS Stetham and the dry cargo ship USNS Caesar Chavez sailed through the Taiwan Strait, in a show of support for Taiwan, U.S. regional partner.