Since May, Luttig has been advising Boeing's board and handling the company's legal efforts related to the crashes of two 737 MAX jets that killed 346 people. The MAX has been grounded since mid-March.
Luttig was a close adviser to Muilenburg, who resigned Dec. 23.
"Judge Luttig is one of the finest legal minds in the nation and he has expertly and tirelessly guided our company as general counsel, counselor, and senior advisor," said interim Boeing President and CEO Greg Smith.
"We are deeply indebted to Judge Luttig for his extraordinary service to Boeing over these nearly 14 years, especially through this past, challenging year for our company," Smith added in a company statement.
Luttig’s departure would make the fourth from Boeing’s executive council, The Wall Street Journal noted. The others are Muilenburg; Kevin McAllister, who was removed as head of the company’s jetliner business; and Anne Toulouse, who plans to step down as senior vice president of communications.
Muilenburg, meanwhile, could be in line for a $6.8 million severance payment and a more than $30 million benefit plan based on his employment contract, according to company filings with the Securities and Exchange Commission.
How much, if any, of this package Muilenburg walks away with will likely hinge on the former CEO's negotiations with the Chicago aerospace giant and on exactly how it classifies his departure.