Now in its sixth day, the search for the Malaysia Airlines Boeing 777 and its 239 passengers and crew has exposed tensions between Beijing and Kuala Lumpur, with Chinese officials from Premier Li Keqiang on down criticising Malaysia's handling of the crisis. China has sent a team of envoys and investigators to Malaysia to deepen its involvement.
While Beijing's concerns reflect, in part, public anxiety over the fate of more than 150 Chinese on board Flight MH370, the search comes at a time when China has been flexing its muscles in the disputed South and East China Seas.
One aerospace and defence industry source with years of experience in the region said the Chinese response would stick in the minds of its neighbours.
"This is a demonstration of force in a peaceful context," said the source, who declined to be identified because he was not authorised to speak to the media.
China has deployed four warships, four coastguard vessels, eight aircraft and trained 10 satellites on a wide search area far from mainland China. Chinese media have described the ship deployment as the largest Chinese rescue fleet ever assembled.
The missing plane's last reported contact with civilian radar was near the mouth of the Gulf of Thailand, which opens into the South China Sea. The aircraft was bound for Beijing after taking off from Kuala Lumpur.
Chinese Foreign Ministry spokesman Qin Gang on Monday acknowledged Malaysia had the "main responsibility" for both the search and the follow-up investigation. He added, however, that Beijing had a responsibility not only to participate but to "demand and urge" Malaysia to step up its efforts.
ONCE WARM TIES
Ironically, China's ties with Malaysia had been among its warmest in the region despite a dispute over territory in the South China Sea.
However, Chinese warships staged a show of sovereignty just two months ago at the James Shoal, a submerged reef about 80 km (50 miles) off Malaysia's Borneo island state of Sarawak - and some 1,800 km (1,125 miles) from mainland China.
Beijing regards those waters as its southernmost territory, the bottom of a looping so-called nine-dash line on maps that comprise 90 percent of the South China Sea. The Philippines, Vietnam, Brunei and Taiwan are also in dispute with Beijing over parts of the ocean.
The People's Liberation Army Navy (PLAN) deployment at the shoal was led by one of its three state-of-the-art amphibious assault ships. Two of those 20,000-tonne vessels - the Kunlunshan and the Jingangshan - have joined the search for the missing plane.
"The Chinese are drawing the conclusion that these guys are not ready for prime time," said Ernie Bower, a Southeast Asia specialist at Washington's Center for Strategic and International Studies, referring to Malaysia.
The fruitless search has shone the spotlight on a series of fumbling news conferences by Malaysian officials and a long delay in divulging details of the military's tracking of what could have been the plane hundreds of miles off course.
Malaysian government officials say they are coping as best they can with a highly complex crisis.
Regional naval officials and analysts said one of the big questions now was what the protracted search - and China's growing concerns over Malaysia's response - would mean for Beijing's approach to the region in future.
While many foreign experts see Beijing's deployment as robust, Chinese state television and other media reports have referred to a lack of Chinese capabilities to conduct extended search and rescue operations far from the mainland coast.
More facilities would be needed for dealing with humanitarian disasters, one Chinese expert said, even though China had expanded listening posts, ports and runways at its facilities in the disputed Paracel and Spratly archipelagoes of the South China Sea.
"This will not be the last time. China has a responsibility and calling to join in," said Ruan Zongze, a former Chinese diplomat with the China Institute of International Studies, a think tank affiliated with the Foreign Ministry.
The Chinese effort is already sparking concern among the public in Vietnam, where battles over sovereignty against China go back decades.
Social media has been active with postings, comments and deep suspicion about the presence of Chinese planes and warships near the Vietnamese coast.
Deputy Transport Minister Pham Quy Tieu, head of Vietnam's search and rescue effort, told Reuters that China had asked permission for its ships and planes to enter Vietnamese territory and that Hanoi remained in "total control".
"China only flies and searches at high altitude, its boats never go deep inside our waters. So we are not concerned about breaches of our sovereignty," Tieu said.
"NEW HISTORIC MISSIONS"
Ian Storey, an expert on ties between China and Southeast Asia, said Beijing's deployment reflected its regional military build-up and the PLA's so-called "new historic missions", which included protecting Chinese nationals abroad.
The crisis would bolster the case of those in China who believe that as the country's global interests expand, its defence budget should grow to protect those interests, added Storey, from the Institute of South East Asian Studies in Singapore.
China this month announced a 12.2 percent rise in military spending to 808.23 billion yuan ($131.57 billion) for 2014, but gave no breakdown of how the money would be spent.
Its military spending, second only to the United States, has allowed China to create a modern force that is projecting power not only across the East and South China Seas, but further into the western Pacific and Indian Oceans.
Bower said the confused search highlighted weak military cooperation in Asia and the need for better coordination between Washington and its Asian allies and partners.
A long-running effort by the Association of South East Asian Nations (ASEAN) to tie China to a binding agreement on measures to lower tensions in the South China Sea includes search and rescue cooperation.
Such cooperation is part of the discussions, and ASEAN envoys said this could be accelerated outside the broader and more sensitive talks.
"Since we don't have that collaborative effort well established yet, I think the Chinese are, whether intentionally or unintentionally, sending a message to their citizens that Malaysia is a small country that's not able to manage well," said Bower. (Additional reporting by David Brunnstrom in Washington, Tim Hepher in Paris, Ben Blanchard and Megha Rajagopalan in Beijing, Grace Li in Hong Kong and Nguyen Phuong Linh in Ho Chi Minh City. Editing by Dean Yates.)