The Chinese have gotten a new jetliner off the ground that some American aircraft industry officials say should never rightfully have been taken off the drawing board.

The Americans claim that the Chinese-built craft that reportedly was test-flown Tuesday from Shanghai to Peking was copied from one of 10 Boeing 707 jetliners bought by China in 1972.

Chinese engineers secretly have been working on the plane for at least two years, according to U.S. aircraft company representatives who saw it in a factory outside Shanghai last year.

Although the 178-seat plane officially is named the Y10, some Chinese who noted its similarity to the Boeing craft call it the "708." American experts were told by Chinese engineers last year that the Y10 could not fly because they had failed to establish the plane's center of gravity.

But a Shanghai newspaper today displayed a picture of the Chinese plane lifting off a runway and declared that this "plane of our design and making" successfully journeyed to Peking.

"At 2:15 p.m. the plane landed smoothly in Peking with the few dozen Chinese passengers feeling good," reported the front-page article. "The crew said happily, 'Everything is fine.' "

When China's plans for the Y10 became publicly known 18 months ago, U.S. business executives questioned whether the direct copy of a U.S. aircraft design without a license violated American export-control laws.

Other foreign business executives in Peking said the project confirmed their fears that China intended to buy only a few pieces of high technology from abroad, learn how to copy them and thereby limit foreign purchases.

"The Chinese want to be in a position to produce everything they need," said an American businessman here. "We want to be in the position of selling them everything we can. Obviously there's a contradiction."

Barry Grossman, an attorney with the U.S. Commerce Department's Office of Legislation and International Affairs in Washington, said today that the United States and China had been carrying on "a significant number of personnel exchanges" with the aim of establishing a patent law in China. He said efforts to persuade the Chinese that such a safeguard is attractive to foreign investment had been successful.

A Western diplomat who deals with the problem of foreign business executives in China said that every company trying to enter the market here has to "weigh the risk of getting ripped off."

Ironically the potential for industrial piracy in China is considered lowest for sophisticated technology, such as aircraft, which requires a level of qualified personnel and equipment thought to be years ahead of Chinese capabilities.

Boeing officials have downplayed the Y10 reports, saying they have little worry about reproduction of a plane designed in 1954.

A spokesman for Boeing in Washington, when asked about the Y10, said, "That's a Chinese development." He said the company had neither details about nor objections to the new plane. "We find them very good customers," he said.

Boeing has avoided raising the issue with the Chinese, officials have said, because they do not want to make customers feel uncomfortable. Boeing also has sold China three 747 jetliners and now is competing with McDonnell Douglas for the order of a smaller civilian aircraft.

Chinese officials with responsibility for the plane's production have denied that it is modeled after the 707. They could not be reached today.