The first built-in-China aircraft carrier has completed a third sea trial but needs more time to reach combat readiness, with the coronavirus pandemic taking a toll on testing schedules, according to military observers. The Shandong finished a 23-day voyage in the Bohai Sea and returned to its home port of Dalian in the northeast province of Liaoning on Sunday. China military: how Beijing is pushing forward its plan for a powerful, modern armed forces The trial was completed just a few days before the first anniversary of the carrier’s commissioning and amid reports that the vessel might reach initial operational capability (IOC), the basic level of combat readiness, as early as the start of next year. But a military insider said the pandemic had dragged out training schedules, with the crew forced to spend more time on pandemic control measures. “All sailors should be quarantined for two weeks before boarding the ship ... Another three weeks will be spent in isolation after their return,” the insider said, declining to be named because of the sensitivity of the issue. “Whether the Shandong can complete all tests and meet IOC in the beginning of next year will depend on the pandemic.” Hong Kong-based, pro-Beijing newspaper Wen Wei Po reported on Monday that commercial satellite images showed for the first time, a submarine sailing near the Shandong during the trial. Observers said this was probably part of training to improve the carrier’s ability to give coverage to the country’s nuclear-armed ballistic submarines. Some analysts have speculated that submarines have routinely accompanied the Shandong since its first voyage. “It’s routine for an aircraft carrier to train with submarines in sea trials because the carrier needs to cover subs,” Beijing-based military expert Zhou Chenming said. “But it is still too early to estimate when the Shandong will be combat ready.” China has expanded the shipyard where its nuclear submarines are built, satellite imagery shows Lu Li-shih, a former instructor at Taiwan’s Naval Academy in Kaohsiung, said the presence of a nuclear submarine with the Shandong carrier might be a signal to the United States about its nuclear strength. “China’s Type 094 nuclear ballistic missile submarines are needed to bolster its nuclear deterrence. If they can sail close to Hawaii, the subs can hit anywhere in the continental United States,” Lu said. “But the subs need coverage from aircraft carrier strike groups. “The first appearance of a nuclear submarine with the Shandong carrier could mean good results in the latest sea trial.” Taiwan starts building its own submarines despite questions over ability to deter attacks from mainland China China has already built six Type 094, or Jin-class, nuclear ballistic missile submarines, with each vessel capable of being armed with 16 JL-2 missiles that can travel up to 7,000km (4,350 miles). The frame design of Shandong is based on its sister ship, the Liaoning , a half-built Russian Kuznetsov-class heavy aircraft-carrying missile cruiser that Beijing bought from Ukraine in 1998 and spent more than eight years to refit. The Liaoning is so far the only Chinese aircraft carrier with IOC. But the Shandong’s interior construction, weapons systems and training operations are closer to those of the US’ Nimitz-class aircraft carriers, which team up with destroyers, frigates, attack submarines and supply vessels to form a strike group. State broadcaster CCTV reported on Monday that the Shandong’s trial in the Bohai Sea included J-15 fighter jets practising take-offs and landings.