Qatar Airways doubled its deal for Boeing 777-9Xs Wednesday, firming a previous commitment for 50 aircraft and adding new purchase rights for an additional 50 of the widebodies.

The new deal, signed at the Farnborough Airshow, also includes a letter of intent for four firm and four option 777 freighters. At list prices, the total deal is worth $40.1 billion ¬– $37.7 billion for the 777Xs and $2.4 billion for the 777Fs.

Qatar became a launch customer for the 777X at the Dubai Airshow in November when it announced a commitment for 50 aircraft.

Speaking Wednesday at the signing ceremony for the revised deal, Qatar Airways CEO Akbar Al Baker said he was doubling the number of 777Xs because of his confidence in Boeing and the 777 and because some of the option aircraft will go to airline customers of the leasing company that Qatar is setting up. He added that all 50 of the firmed 777Xs will be for Qatar Airways.

Deliveries will start in 2020.

The Boeing 777X is sole-source powered by the GE Aviation GE9X engine and includes an all-new composite wing with a folding, raked wingtip and an optimized span for an aircraft that Boeing says will be 12% more fuel efficient than others in its class.

Al Baker indicated Wednesday that negotiations for the deal went down to the wire during this air show, with fierce haggling over the engine price in particular. But he also pointed out that once he commits, he remains true to his word.

“We are very serious; every single purchase right we have done, we have exercised,” he said.

The Doha-based, oneworld carrier caused some controversy this week by making a last-minute decision not to bring an Airbus A380 to Farnborough because it is not satisfied with the cabin quality of the first three of 10 A380s it has on order.

“We are a very demanding customer,” Al Baker said Wednesday. “We intend to take all 10 of the A380s but only if they meet all or our standards, specifications and requirements. It’s as simple as that.”

Qatar did bring an Airbus A350-900 and an Airbus A320 to the show, however. The carrier is launch customer for the A350, with first delivery scheduled for late 2014. Al Baker said the expanded 777X deal would not affect his commitment to the A350 orders. “We have already firmed those orders and when we sign for something we don’t walk away unless the manufacturer screws up the airplane.”