Boeing won a major vote of confidence at the Paris Airshow on Tuesday as British Airways owner IAG signed a letter of intent to buy 200 of its 737 MAX jets that have been grounded since March after two deadly crashes.

News of the deal, worth more than $24 billion at list prices, sent shockwaves round the world's largest air show which had struggled to find its rhythm amid the 737 MAX crisis and concerns about an economic slowdown.

Airbus, the current supplier of IAG's British Airways and Vueling brands, was stunned by the announcement which came months after it lost a major BA wide-body aircraft order to its U.S. rival. Industry sources said the European company had not been offered a chance to bid.

"We have every confidence in Boeing and expect that the aircraft will make a successful return to service in the coming months," IAG Chief Executive Willie Walsh said of the 737 MAX, announcing the first deal for the plane since its grounding.

Boeing's top-selling aircraft has been taken out of service worldwide since an Ethiopian Airlines 737 MAX crashed in March, five months after a Lion Air 737 MAX plunged into the sea off Indonesia. A total of 346 people died in the two disasters.