U.S. planemaker Boeing said on Monday it sold 100 new 737 MAX-7 jets to long-time customer Southwest Airlines, in its biggest order win since the aircraft's safety ban was lifted in the United States last year.

The order signals the budget airline's show of confidence in Boeing's 737 MAX jets, ending speculation of a shift to jets made by European plane maker Airbus -- which would've been a massive blow to Boeing.

The COVID-19 outbreak compounded troubles for the planemaker, forcing it to cut production after the nearly two-year grounding of the 737 MAX family, following fatal crashes in 2018 and 2019.

Under the deal, Boeing could build more than 600 new 737's for Southwest through 2031.

Each 737 MAX-7 carries a list price of roughly $100 million, though such jets usually sell for less than half their official value due to market discounts, aircraft industry sources have said.

Shares of Boeing were up 3% in morning trade on the news.