China is building a runway on the disputed Antelope Reef in the South China Sea, according to a Reuters exclusive published on October 2, citing satellite images.

Images captured on September 25 by Vantor show land reclamation, grading and gravel work on a runway strip, along with cranes and construction activity. Analyst Ben Lewis of PLATracker estimated the project could be complete by mid-2027.

Beijing describes its work on the reef as civilian, saying it supports weather observation and research. But the scale of construction makes it China’s biggest expansion in the South China Sea in a decade, according to analysts.

Antelope Reef is claimed by several countries, and the militarization of disputed reefs has long been a source of tension in the region. The United States and its allies regularly conduct freedom-of-navigation patrols in the area.

China has built military facilities on several artificial islands in the Spratly chain since 2013. The new runway would extend the reach of Chinese aircraft over the disputed waters.