BAE Systems yesterday said it had decided to exercise an option to speed up the sale of its 20 per cent stake in Airbus to the plane maker's majority owner, EADS.
"BAE confirms it has served on EADS a formal notice of exercise of its put option," BAE said in a statement.
The firm, which analysts said would generate as much as £4.5 billion for fresh acquisitions from the sale, said on May 2 it would use the put option if it could not reach an agreement with EADS.
Under the process, investment banks working for the two sides have two weeks to negotiate a price.
Should they fail to agree, the wording of their deal calls for another investment bank to step in and arbitrate.
EADS owns the other 80 per cent of Airbus and has long expressed an interest in BAE's stake should it want out.
"EADS retains the right to pay in cash, in shares or in a mixture of both," EADS said in a separate statement, adding that the companies would seek to finalise their negotiations in the coming weeks.
Meanwhile US manufacturer Boeing could make an announcement as early as this summer on whether it will double production capacity of its fast-selling 787 Dreamliner - a major source of work for aerospace component firms in the West Midlands.
The mid-sized 787 is sold out from 2008 - the first year of delivery - until 2010, said Randy Baseler, Boeing's vicepresident of marketing for commercial airplanes.
Speaking from the company's offices in Tel Aviv, he added: "There are still a lot of people who want planes.
"We are studying a production increase on the 787. We could make an announcement as early as this summer."
Boeing officials said the company was looking at adding a second production line but they would not comment on where it might be.
The 787, which will replace the 767, makes use of composite materials to reduce weight.