Two private-jet operators early Monday announced news about their acceptance of cryptocurrency, raising yet again questions about the usefulness of digital currency both for luxury spending and everyday shopping.

Clearwater, Fla.-based Hera Flight said it has started accepting Bitcoin, Ethereum, and other cryptocurrencies for charter flights. Meanwhile, Paramount Business Jets in Leesburg, Va., reported what it called a “notable increase” in the number of its clients relying on cryptocurrency to pay for flights, without specifying a number.

Paramount says it has been taking crypto since late last year, with Bitcoin and Ethereum as the most frequently used coins. It cites “lower fees” for acceptance of…