'Helping the motherland'
Chung was employed by the Rockwell International defence firm from 1973 until its defence and space unit was acquired by Boeing in 1996.
Formerly from China and now a naturalised US citizen, he held secret security clearance when he worked at Rockwell and Boeing on the space shuttle programme, officials told Reuters news agency.
At one point, Chung allegedly wrote in a letter to Chinese officials that he wanted to "contribute to the motherland," the US justice department said.
If convicted he faces up to 100 years in prison.
Boeing said on Monday that they had been co-operating with the government on the case.
In the second case, Tai Shen Kuo, a New Orleans businessman, is accused of working with an unnamed Chinese official to obtain secret documents from Gregg William Bergersen, a US defence department employee.
"It's a threat to our national security and to our economic position in the world"
Kenneth L Wainstein, US assistant attorney general for national security
The two cases have no connection and US officials said it was a coincidence that they were both charged on the same day.
A third person, Yu Xin Kang, a Chinese citizen now resident in the US, is accused of acting as a "conduit of information" between Kuo and the Chinese official, the AFP news agency reported.
US officials said the data outlined every planned US sale of weapons or other military technology to Taiwan for the next five years.
According to court documents, the alleged spying took place over a two-year period from January 2006 to February 2008.
Kuo is accused by the justice department of having held a series of meetings with Bergersen in northern Virginia, Charleston, South Carolina, and Las Vegas.
On some occasions, Bergersen, a weapons systems policy analyst, "received undetermined cash payments from Kuo in exchange for information and documents he provided," a justice department statement said.
Kenneth L Wainstein, assistant attorney general for national security, said the arrests marked the latest attempts by China to gain top secret information about US military systems and sales.
China, he said, was "particularly adept, and particularly determined and methodical in their espionage efforts."
"The threat is very simple," he told reporters.
"It's a threat to our national security and to our economic position in the world; a threat that is posed by the relentless efforts of foreign intelligence services to penetrate our security systems and steal our most sensitive military technology and information."