With the death of  Jerry York in March and the forced departure of Google (GOOG) CEO Eric Schmidt in August 2009, Apple (AAPL) found itself with a couple empty seats in its board room.

On Wednesday it announced that it had reached into the aerospace industry to fill one of them.

Dr. Ronald D. Sugar, 61, the former chairman of the board and CEO of Northrop Grumman (NOC), will serve as the chair of Apple’s audit and finance committee.

An electrical engineer by training (BS, MS, PhD UCLA) and a former chief financial officer, Sugar has worked for more than four decades in a high-tech industry, but one — unlike Apple’s — heavily dependent on government contracts.

“I have always had enormous admiration for the people of Apple,” said Sugar in a prepared statement. “It is a special privilege to serve on the board of such an amazing company.”

The choice was greeted positively by analysts contacted by Fortune. “Sugar’s background certainly provides some gravitas,” said Hudson Square’s Daniel Ernst. “Apple has moved from feisty competitor to one of the biggest companies in the world by market capitalization – and therefore it certainly helps to have the advice and counsel of those who have come from there.”

Apple’s press release below the fold.

Ronald D. Sugar Joins Apple’s Board of Directors

CUPERTINO, California—November 17, 2010—Apple® today announced that Dr. Ronald D. Sugar, former Chairman of the Board and CEO of Northrop Grumman Corporation, was appointed to Apple’s Board of Directors. Dr. Sugar will serve as the Chair of the Audit and Finance Committee.

“Ron is an engineer at heart, who then became a very successful business leader. We are very excited to welcome him to Apple’s Board,” said Steve Jobs, Apple’s CEO. “In addition to having been the CEO of a high-tech Fortune 100 company, Ron has a Ph.D. in engineering and has been involved in the development of some very sophisticated technology.”

“I have always had enormous admiration for the people of Apple,” said Sugar. “It is a special privilege to serve on the board of such an amazing company.”

Dr. Sugar served as Chairman and Chief Executive Officer at Northrop Grumman Corporation from 2003 until his retirement in 2010. Previous to Northrop, he held executive positions at Litton Industries and TRW Inc., where he served as chief financial officer.

He is a member of the National Academy of Engineering and a fellow of both the American Institute of Aeronautics and Astronautics and the Royal Aeronautical Society. He is a director of Chevron Corporation, Amgen Inc. and Air Lease Corporation, and serves as a senior advisor to the private investment firm Ares Management LLC.

He is a trustee of the University of Southern California, where he also holds the Judge Widney Chair as Professor of Management and Technology. He is a member of the boards of UCLA Anderson School of Management, the Los Angeles Philharmonic Orchestra and several other philanthropic organizations focused on children and education.

He graduated summa cum laude in engineering in 1968 from the University of California, Los Angeles, where he also received master’s and doctorate degrees in the same field. He subsequently completed executive programs at Stanford, Wharton and Harvard.

Apple designs Macs, the best personal computers in the world, along with OS X, iLife, iWork, and professional software. Apple leads the digital music revolution with its iPods and iTunes online store. Apple is reinventing the mobile phone with its revolutionary iPhone and App Store, and has recently introduced its magical iPad which is defining the future of mobile media and computing devices.

On the board, Sugar joins Steve Jobs, former Vice President Al Gore; JCrew CEO Millard Drexler, former Intuit CEO Bill Campbell, Avon CEO Andrea Jung and Genentech Chairman Arthur D. Levinson.

[Follow Philip Elmer-DeWitt on Twitter @philiped]