China used the technology it purchased from a United States company to develop its first attack helicopter.

Major defense contractor United Technologies and two subsidiaries on Thursday acknowledged covering up the illicit sale of sensitive military software to China, technology it used to develop its first attack helicopter.

Federal prosecutors announced criminal charges against the firms and a fine of more than $75 million for what they called a violation of U.S. export laws. Justice officials said the software sold to China posed a risk to American troops overseas and U.S. allies.

Connecticut-based United Technologies, which reported net sales of $58 billion in 2011, will pay the fine, along with Pratt & Whitney Canada and Hamilton Sundstrand, as part of a settlement for lying to the government and delaying disclosures about the illegal exports, officials said.

China’s acquisition of military technology from U.S. suppliers is prohibited under an arms embargo imposed in 1990, after the Tiananmen Square massacre.

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Under the deferred prosecution deal, an independent monitor will watch the three firms for two years. They face criminal prosecution or additional fines if they further violate export laws.