Vietnam is responding to China’s construction of military facilities in the Spratly Islands in the South China Sea by modestly expanding its own capabilities in the disputed chain.

New imagery published by the Asia Maritime Transparency Project shows that Hanoi is significantly upgrading its sole runway in the South China Sea—at Spratly Island—and constructing new hangars at that location.

“This is a familiar pattern for Hanoi,” said a report on the subject from AMTP. “Even amid reduced diplomatic tensions, Vietnam continues to modernize its military and seek closer security ties with Japan, the United States, and India in preparation for future Chinese assertiveness in disputed waters.”

The South China Sea situation has implications for global shipping and trade, as thousands of ships transit those waters every day, connecting markets and goods in East Asia with the Middle East and Europe. An $5.3 trillion in annual trade transits those waters, $1.2 trillion of which begins or ends at U.S ports.

A United Nations arbitration tribunal in July ruled in favor of the Philippines in a case that nation brought against China over territorial claims in the South China Sea. China claims exclusive territorial rights over most of the area. China boycotted the tribunal and refused to accept its deterimination.

Reuters recently reported that Vietnam had deployed surface to air missile platforms to the Spratlys. Hanoi has not confirmed those reports, but, AMTP commented, “such countermeasures should not be surprising in light of the significant air power that China will soon project over the Spratlys.”

Vietnam has lengthened the runway at Spratly Island from less than 2,500 feet to about 3,300 feet. Continued reclamation and construction will likely extend this to more than 4,000 feet.

Vietnam is also constructing two large hangars and can accommodate the Vietnamese air force’s PZL M28B maritime surveillance aircraft and CASA C-295 transport planes. Any of Vietnam’s combat aircraft could also make use of the new runway, but the islet would have limited use for fighter jets. “

“By contrast,” noted the report, “China’s three largest artificial islands now boast enough hangar space for 24 fighter jets each.”

Vietnam has now added about 57 acres of land at Spratly Island though its activities remains modest compared to China’s.

The AMTP report said Vietnam is likely to use of its enhanced runway and hangars to patrol the Spratlys. While Vietnam’s military capabilities are no match for China, “Hanoi seems determined,” the report concluded, “to better monitor and, if the reported missile deployments are true, defend its claims.”