Two Chinese tactical fighters intercepted a U.S. Navy reconnaissance aircraft over the South China Sea earlier this week, a Pentagon spokeswoman announced Wednesday.

The U.S.EP-3E Aries, a propeller driven aircraft capable of intercepting radio communications, was flying in international airspace Tuesday when it was approached by two Chinese J-11 jets. The Chinese aircraft came within roughly 50 feet of the U.S. plane and were so close that the U.S. EP-3E was forced to descend to avoid collision, according to a report from the Associated Press.

The Pentagon described the incident as “unsafe.” In 2001, a U.S. EP-3 collided with a Chinese J-8, killing the pilot and forcing the American plane to make an emergency landing in China.

“Over the past year, [the Pentagon] has seen improvements in [Chinese] actions, flying in a safe and professional manner,” Baldanza said in a written statement.

Earlier this month, Chinese jets and warships scrambled to intercept a U.S. destroyer that sailed within 12 miles of a disputed island in the South China Sea. The island, known as Fiery Cross Reef and situated in the Spratly Island Chain, was once a cluster of rocks before being turned into a fully functional military base complete with a port and runway by the Chinese.

The small island has been claimed by China, Taiwan, Vietnam and the Philippines and is emblematic of the current struggle between countries attempting to secure portions of the resource-rich waters of the South China Sea.

While the United States has maintained its distance in the territorial disputes, the Pentagon has consistently said it will not be deterred by China’s militarization of the region.

“The United States will fly, sail, and operate wherever international law allows,” Cmdr. Bill Urban, a Pentagon spokesman, said earlier this month. “That is [as] true in the South China Sea as in other places around the globe.”