A Chinese national and permanent U.S. resident pleaded guilty in federal court Monday to two counts of stealing sensitive military documents from United Technologies and transporting them to China.

Officials alleged Yu Long “admitted to stealing and exploiting highly sensitive military technology and documents” to benefit not only China, but to further his own career, said acting Assistant Attorney General for National Security Mary B. McCord.

According to the 30-page plea agreement, Long worked as a senior engineer and scientist at the East Hartford-based United Technologies Research Center (UTRC) from 2008 to 2014. Among other projects, he worked on F119 and F135 engines. During 2013 and 2014, the government maintains, he “was recruited” in China by the Chinese Academy of Science (CAS) and others, “during which he leveraged information he had obtained while working at the company [UTRC] to seek employment at state-run universities in China, culminating in his travel to China in the possession of voluminous documents and data containing highly sensitive intellectual property, trade secrets and export controlled technology, which he had unlawfully stolen from the company.”

In December 2013, Long agreed in principle to join the Shenyang Institute of Automation (SIA), a state-run university in China affiliated with CAS. On Dec. 24, 2013, Long emailed several UTRC documents to the SIA-CAS director. In May 2014, Long left UTRC and joined SIA a month later. In July 2014, digital evidence and forensic analysis indicated Long brought with him and accessed in China a UTRC external hard drive that had been issued to him and that he unlawfully retained, prosecutors charged.

According to the plea, Long returned to the U.S. in August 2014 and was arrested shortly before he was to head back to China in November 2014. During Long’s layover in Newark, New Jersey, U.S. Customs and Border Protection officers inspected his checked baggage and discovered sensitive, proprietary and export-controlled documents from another defense contractor: Rolls Royce.

Further investigation determined the U.S. Air Force had convened a consortium of major defense contractors, including Pratt & Whitney and Rolls Royce, to work together to see whether they could collectively lower the costs of certain metals used. As part of those efforts, members of the consortium shared technical data, subject to restrictions on further dissemination. Rolls Royce reviewed the documents found in Long’s possession and confirmed it provided documents to members of the consortium. A review of UTRC computer records indicated Long had printed the documents while employed at UTRC, according to the plea.

Long, who has been detained in the U.S. since his arrest on counts of stealing sensitive military documents, faces up to 35 years in prison if convicted on both counts. In addition, he faces fines totaling more than $6 million. He will be sentenced by U.S. District Judge Robert N. Chatigny in Hartford, but the sentencing date hasn’t been scheduled, the government said.

Long is being represented by William F. Dow of the New Haven-based Jacobs & Dow and Marc Agnifilo of the New York City law office of Brafman & Associates. Dow declined to comment and Agnifilo could not be reached for comment.

The case was investigated by numerous agencies, including the FBI in New Haven and the Office of the U.S. Attorney for the District of Connecticut. It is being prosecuted by Assistant U.S. attorneys Tracy Lee Dayton and Stephen B. Reynolds of the District of Connecticut, and trial attorneys Brian Fleming and Julie Edelstein of the National Security Division’s Counterintelligence and Export Control Section.