TIMELINE: Recent spy scandals involving China and U.S.

(Reuters) - A former Boeing engineer was arrested on Monday on charges of stealing trade secrets for China related to several aerospace programs, including the Space Shuttle, the U.S. Justice Department said.

It also announced a separate case in which a U.S. Defense Department official and two others were arrested on Monday on espionage charges involving the passing of classified U.S. government documents to China.

Following is a chronology of some recent spy cases involving China and the United States.

1999 - Los Alamos National Laboratory, where the first U.S. nuclear bombs were developed in the 1940s, comes under fire over security after U.S. prosecutors charge scientist Wen Ho Lee with 59 counts of illegally downloading nuclear weapons data onto portable tapes and non-secure computers. Lee was never charged with espionage despite early allegations of Chinese snooping on Los Alamos, and the case against him collapsed in 2000, when all but one charge against him was dropped and a federal judge apologized for keeping him in solitary confinement for nine months.

March 2000 - China has intensified its spying operations in the United States over the past decade, collecting military and economic secrets and seeking to exert influence over policy decisions in Washington, according to a report by two U.S. intelligence services.

October 2000 - The Pentagon is hiring 450 counterintelligence specialists to protect defense secrets after learning that China obtains classified U.S. missile technology, the Washington Post reports, quoting senior defense officials.

November 2000 - China dismisses allegations in a book by a Washington Times reporter about Chinese spying on U.S. nuclear secrets as "sheer fabrication" and accuses the author of still living in the Cold War era. The book, "The China Threat" by Bill Gertz, alleges Beijing had 37 spies ferreting out U.S. nuclear secrets in the mid-1990s and includes extensive excerpts from a U.S. intelligence report.

January 2002 - Loral Space & Communications Ltd., under investigation since 1997 for allegedly leaking sensitive missile technology to China, says it reaches a settlement with the U.S. government that could let it resume long-delayed satellite exports to China. Loral said it had agreed to pay a civil fine of $14 million to the State Department over seven years without admitting or denying the government's charges.

November 2007 - China hits back at a U.S. congressional panel report, calling its claims of trade manipulation and high-tech espionage by Beijing "insulting" and "misleading." The U.S.-China Economic and Security Review Commission's report said China presented an array of threats to Washington, including "currency manipulation," computer espionage, and murky military modernization plans.