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China building up its military presence in the South China Sea amid rising tensions with U.S.

During a high-stakes U.S. surveillance flight, NBC News’ Janis Mackey Frayer gets a rare chance to see China’s military buildup just weeks after the U.S. shot down the Chinese spy balloon. A Chinese fighter jet came within 500 feet of the U.S. aircraft, as tensions flare up between the two superpowers.