Saudi Arabia's two state-owned airlines have ordered a total of 78 Boeing 787 Dreamliners, with an option to purchase 43 more.
The firm order is split evenly between existing carrier Saudia and upstart airline Riyadh Air.
The orders are part of an aggressive effort by the Saudi state to turn the long-insular kingdom into a major tourism destination and global connecting airline hub that serves 330 million flyers annually by 2030.
If the airlines go through with all 121 firm and optional orders it would be Boeing's fifth-largest order in value. The deals are valued at nearly $37 billion, Secretary of State Anthony Blinken said in a statement extolling the significance of the sales to the U.S. economy.
The orders are to be paid for by Saudi Arabia's sovereign wealth fund.
Riyadh Air has ordered 39 787-9 Dreamliners and has options on 33 additional 787-9s. The new carrier would be based at King Salman International Airport, a sprawling facility that is in the planning stages.
Saudia, which is based in Jeddah, has ordered 39 Dreamliners and secured options on 10 more. The order is split between the 787-9 and the larger 787-10.