From the Document: "On September 24, 2021, the U.S. Air Force awarded a contract [hyperlink] to Rolls-Royce, Indianapolis, IN, for 608 new engines to replace the TF33 engines powering the B-52H Stratofortress bomber fleet, in a contract running up to 17 years. The initial contract is for $500.9 million, but with spare engines, technical data, support equipment, and sustainment, the contract could ultimately be worth $2.6 billion, and may include 650 engines. Rolls-Royce has 18 months to deliver initial engines. The Air Force currently operates 76 B-52Hs [hyperlink], the most recent of which was built in the 1960s. The Air Force now expects to operate them until 2050. The last TF33 engine was built in 1985 [hyperlink]. (For more on the B-52 fleet, see CRS [Congressional Research Service] Report R43049, 'U.S. Air Force Bomber Sustainment and Modernization: Background and Issues for Congress'.)"
CRS Insight, IN11413
Congressional Research Service: https://crsreports.congress.gov/