United CEO Says Premium Push Runs Up Against Planemaker Woes

United Airlines Holdings Inc. Chief Executive Officer Scott Kirby says a lack of new aircraft is impeding his plans to modernize the fleet and cash in on booming premium travel.

Engine shortages and supply-chain snarls have slowed deliveries from Airbus SE, while Boeing Co. struggles with certification delays and production curbs on models like the 777X and 737 Max 10 jet, which United had ordered in large numbers.