Boeing said on Thursday that it planned to take over the commercial jet business of the Brazilian aerospace company Embraer, a move into smaller jetliners that mirrors a deal last fall by rival Airbus to join in a partnership with Bombardier.

Boeing would own 80 percent of Embraer’s commercial aircraft and services arm, which the companies said was worth $4.75 billion. Embraer would own the rest.

Under the memorandum of understanding announced by both companies, management would be based in Brazil, but the venture will be controlled by Boeing, which is based in Chicago. The companies also said that they would form another joint venture focused on “new markets and applications for defense products and services,” such as Embraer’s KC-390 military transport plane.

The two companies have collaborated on projects for decades and have been in talks since last year on a partnership for planes with 70 to more than 450 seats and for freighters.