United Airlines expects that three quarters of its fleet will be new-generation by 2030 as it converted previous options and purchase rights into firm orders for 50 Boeing 787-9 Dreamliners.
The US carrier also secured new options for up to 50 more B787s.
The airline also confirmed firm orders for 60 Airbus A321neos (pictured) and purchase rights for an additional 40 of the single aisle aircraft at the end of the decade.
The fleet update means that United expects to take delivery of about 800 new and wide and narrow-body aircraft between this year and the end of 2032.
The plan is to fly larger aircraft with more available seats on existing routes.
The 50 new B787-9s ordered will allow the airline to further simplify its international fleet, helping to achieve cost savings.
United already claims to be the largest carrier across the Atlantic and Pacific and now has 150 B787s on firm order – more than any airline in the world.
Chief executive Scott Kirby said: “We’re building a bright future at United and this order takes our already successful United Next plan into the next decade and beyond.
“Our planning and focus on the long term have helped us surge past other airlines that stood still.
“I’m convinced our strategy is the right one as we continue to add new, larger aircraft to take full advantage of our growing flying opportunities both internationally and domestically.”