The disputed waters have been a point of contention between Beijing and Washington. The United States does not recognize China's claims of sovereignty over the man-made islands.
On Thursday, the Pentagon said the bomber was contacted by Chinese ground controllers, but continued its mission undeterred, Reuters reported.
"We conduct B-52 flights in international air space in that part of the world all the time," Pentagon spokesman Peter Cook told a briefing.
"My understanding is there was one B-52 flight, I'm not even sure the date on it, but there was an effort made by Chinese ground controllers to reach out to that aircraft and that aircraft continued its mission…. Nothing changed."
The announcement from the Pentagon comes as tensions are still simmering after Washington sent a US warship within 12 nautical miles of the manmade islands.
On October 27, the USS Lassen sailed near the Spratly islands in a challenge to China's territorial claims in the region.
The Pentagon last week pledged to continue such patrols in the region in accordance with freedom of navigation and international law.
Roughly $5 trillion in trade passes through the South China Sea annually. While China claims over 90% of the region, there are overlapping claims from Malaysia, Taiwan, Brunei, Vietnam, and the Philippines.
