If those planes were deployed, they would greatly complicate China’s disputes with the Philippines and other nations, and add a level of military risk to the United States’s “freedom of navigation” patrols through the area.
Even before the hangars appeared, it was clear to independent military analysts that China’s intention was to use the islands to flex military might in the area.
“We knew from the day they started building those runways,” Mr. Poling said. For China to assert a more benign purpose, he said, would be “like saying you’re building a mansion, but only living on the first floor.”
Evidence of the military hangars emerged a month after an international tribunal at The Hague sharply rebuked China over its behavior in the South China Sea, including its assertion of expansive sovereignty and construction of artificial islands.
The tribunal’s ruling was a response to a landmark case brought by the Philippines, which called it an “overwhelming victory.” Infuriated, China said it would ignore the ruling.
Some analysts cautioned that the hangars were not a response to the ruling and had likely been under construction for some time.
“The foundations may have been laid months ago,” said M. Taylor Fravel, a political science professor at the Massachusetts Institute of Technology and a member of its Security Studies Program.
Mr. Fravel said the hangars are not necessarily inconsistent with the Chinese president’s assertions.
“China has given itself the option to use these reefs as military facilities, but has not decided yet to what degree it is going to use them,” he said. “It creates the option for a robust defense of those places or even a power projection.”