Updated

Finding the missing Malaysian jetliner would be a coup for any of the more than two dozen countries out there looking. But for China and the United States, it's a lot more than that — it has been a chance for the two rival powers in the Pacific to show off what they can do in a real-life humanitarian mission across one of the world's most hotly contested regions.

The hunt has major ramifications for Beijing, which has been rapidly improving its military while aggressively challenging neighbors over territorial disputes. Washington is looking to prove it's still the top dog to allies worried about how seriously it takes the threat China poses to the Pacific status quo.

So far, neither country has come up with anything significant. But they have been vigorously waving their flags.

China has the most at stake and has been taking an unusually high-profile role. Almost immediately after Malaysia Airlines Flight 370 disappeared March 8, China dispatched its largest-ever rescue flotilla to the initial search area in the South China Sea, which Beijing considers its own backyard.

Beijing sent four warships and five coast guard and civilian patrol service vessels, along with helicopters and fixed-wing surveillance aircraft. Among the warships are two of China's largest and most advanced amphibious docking ships. The 20,000-ton vessels are equipped with helicopters and a range of small boats, including up to four hovercrafts.

"On the one hand, China is simply doing its duty in orchestration with other countries," said Ni Lexiong, a military expert at Shanghai's University of Political Science and Law. "On the other hand, this operation offers an opportunity to assess the Chinese navy's willpower, efficiency and ability to carry out operations far from home, especially in comparison with the U.S."

Fresh off a massive relief effort after Typhoon Haiyan devastated the Philippines — which China barely got involved in — the U.S. was once again quick to respond. Within days, the Navy had two destroyers in the South China Sea participating in the search, the USS Kidd and the USS Pinckney. Both are both based in San Diego but were training in the area when the jet disappeared.

Since the flight was bound for Beijing and two-thirds of the passengers were Chinese, the public expects the government and military to pull out all the stops. With more Chinese traveling abroad than ever — 100 million last year, more than double the figure for 2009 — they are increasingly reliant on their government to assist and protect them when overseas, and they are looking for proof that it can fulfill that role.

National prestige is also a huge factor.

Though the U.S. remains the dominant power in the Pacific, China deeply craves that role. Sizable chunks of its defense spending, which has grown significantly over the past two decades to $131 billion, have been devoted to boosting its ability to project force for both military and humanitarian missions.

China's Achilles' heel is its relative lack of experience, not having fought in a major conflict since the end of the Korean War in 1953. Its leaders have been trying to compensate with more realistic training scenarios, including joint maritime search and rescue exercises with other nations.

"Everyone understands, without anything being said, that the U.S. has unmatched search and rescue capabilities that reflect the size and sophistication of its air and naval forces," said Avery Goldstein, a China security expert at the University of Pennsylvania. "China's capabilities in this regard are improving but not yet in the same league, especially for operations at great distance from the Chinese mainland."

Given new clues from radar and satellite data that the missing Boeing 777 turned west and flew on for several more hours, the search has shifted to a vast swath of land and sea stretching from the southern Indian Ocean up to Kazakhstan. That's an area that neither China nor the U.S. has traditionally put much emphasis on, and has forced both to rethink their strategies.

The U.S. Navy decided that long-range naval aircraft were a more efficient way to search such a vast area, so will be relying on P-3 and P-8 planes, while the two destroyers go back to normal duties.

The mission is one of the first on the international stage for the P-8 Poseidon, one of the newest additions to the Navy's air capabilities. The Navy touts the aircraft as the world's most advanced anti-submarine and anti-surface ship reconnaissance plane and says it can cover 15,000 square miles (38,850 square kilometers) in a nine-hour flight.

China, meanwhile, has sent most of its ships involved in the search toward Singapore, where they will split into two groups, one traveling north and the other south. They will be searching two huge blocks of ocean off the coast of Sumatra and near the Andaman Islands — a total area of 300,000 square kilometers (186,000 square miles), or roughly three times the area they searched in the South China Sea.

A big problem for China is its bad blood with virtually all of its neighbors, many of whom are key players in the search. China has territorial disputes with India, Japan, the Philippines and Vietnam, and many other countries in the region are wary of its efforts to exert more control over Pacific shipping lanes that could impact their freedom of trade.

"China is strong in terms of hardware, but it lacks experience and good security ties with regional states," said China expert Li Mingjiang at Singapore Nanyang Technological University. "The U.S. sailors have far better networking with their regional counterparts, making it more possible for the U.S. to play a leading role in the search and rescue effort."

Chinese officials haven't done themselves any favors by criticizing Malaysia's leadership in the search effort. Some saw that as an attempt to shift public attention away from its own shortcomings, and Beijing's weak military-to-military relationship with Malaysia probably exacerbated the issue.

Japan, which is Washington's staunchest ally in Asia and is locked in a tense dispute with China over several small islands, has been watching Beijing's response especially closely. Experts in Tokyo say that while they remain skeptical, there is hope that by coming together with other countries to pursue a common goal, China may learn to work more amiably with its neighbors.

"Some people say China is trying to use the mission as a way to show off its presence, but that also means they are stepping up their efforts and capabilities in disaster relief," said Kyouji Yanagisawa, a former Japanese Cabinet adviser on national security. "This is a search operation and I think it could be an opportunity to cultivate trust among participating countries, rather than conflict."

___

Bodeen reported from Beijing. AP writer Mari Yamaguchi in Tokyo contributed to this report.