United Airlines Holdings Inc. is overhauling its fleet with the biggest jetliner order in company history and an ambitious upgrade for its aircraft cabins, bolstering a push to appeal to more travelers willing to pay for pampering.

The airline agreed to buy 200 Boeing Co. 737 Max jets and 70 Airbus SE A321neo planes, a deal valued at about $15 billion based on estimates by aircraft appraiser Ascend by Cirium. Those planes and other United single-aisle jets will get a revamped cabin with seat-back screens and larger overhead bins, according to a company statement Tuesday.

The plans signal the airline’s intention to step up competition with Delta Air Lines Inc. and American Airlines Group Inc. for premium-seat customers, who demand more creature comforts and typically generate an outsize portion of industry profits. United will use the new planes to reduce its use of smaller regional jets amid an anticipated rebound in corporate demand, which is still stuck at less than half the pre-pandemic level.