Defense giant Northrop Grumman Corp. launched a $5.9 billion unsolicited bid Friday to buy TRW Inc., and TRW called the move "regrettable" since it came just days after its boss announced his departure.

Northrup Grumman announced the move, aiming to boost its aerospace business, only three months after it sealed a deal to buy the country's only builder of nuclear powered aircraft carriers.

"We believe the strategic combination of Northrop Grumman and TRW will provide tremendous value to the shareholders of both companies," said Kent Kresa, Northrop Grumman's chairman and chief executive officer. "Northrop Grumman's electronics and systems integration capabilities, combined with TRW's space and systems expertise, would create a strong contributor to the nation's satellite and missile defense requirements.

Cleveland-based TRW makes space and defense products including spacecraft and satellite technology, defense communications equipment and high-energy lasers.

Los Angeles-based Northrop Grumman would sell TRW's automotive parts business, which account for 60 percent of the company's sales, if TRW accepts Northrop's offer.

Under terms of the offer, Northrop is offering $47 in stock for each TRW share, an 18 percent premium over the company's closing share price of $39.80 Thursday on the New York Stock Exchange. The offer was outlined in a letter dated Thursday to TRW management and released by Northrop on Friday.

TRW said in a brief statement that its board would review the proposal to determine what action will serve the best interests of shareholders and other constituencies.

However, it added, "TRW finds it regrettable that Northrop Grumman has chosen to make this proposal immediately following the unexpected departure of its (TRW's) former chief executive officer, David Cote, and the aberrationally low stock price that resulted."

The offer comes three days after TRW announced Cote had resigned to take the top job at rival Honeywell International. TRW shares have fallen 5 percent since then, after reaching as high of $45.45 in the last year.

Cote, 49, had served for just over six months as chairman, president and CEO of TRW. He spent 25 years before that in various management and leadership positions for GE.

Newport News Shipbuilding Inc., the nation's only builder of nuclear aircraft carriers, agreed in November to a $2.1 billion takeover by Northrop.

With the purchase of Newport News, Northrop is adding a third huge shipyard, with 17,800 workers, to its portfolio -- the company already owns yards in Louisiana and Mississippi that make Navy ships.

Northrop has about 100,000 employees in 44 states and 25 countries. TRW has about 94,000 workers.