The Chinese People’s Liberation Army Navy now has an aircraft carrier, new jet fighters to fly off the flattop and even new submarines and guided-missile destroyers able to protect the refurbished Soviet carrier. And with the successful first sea trials of two new, 590-foot-long fleet oilers — tanker ships designed to keep other vessels fueled, or “replenished,” while sailing long distance — the PLAN could soon be able to deploy all this new hardware beyond coastal waters.

“Replenishment vessel construction rate will be a particularly revealing barometer of the PLAN’s future expeditionary intentions,” wrote Andrew Erickson, an analyst at the U.S. Naval War College. The more new oilers, the farther China will be able to send its new capital ships. Without underway replenishment, most naval vessels can travel only a few thousand miles; with fuel top-offs, they can circle the globe.

The latest, upgraded Qiandaohu-class oilers, also known as Type 903s, were launched at a shipyards in Guangzhou and Shanghai last spring. After additional work, the tankers began sea trials in the China Seas, testing out the vessels’ mechanical systems plus the storage tanks, valves, hoses and other gear for refueling other ships at sea. This week the first of the new Qiandaohus reportedly completed her trials, clearing her for frontline use.