Temperature and pressure measurements indicate that during the first 20 or 30 seconds of an eruption, steam and boiling water shoot through the narrowest part of Old Faithful's vent at the speed of sound.

Source: https://kgab.com/ixp/101/p/wyoming-site-makes-top-10-most-visited-world-wonders-in-the-u-s-list/

The mark has been topped since, with the current record sitting at 1224 km/h – faster than the speed of sound – but Breedlove helped make the land-speed mark a cultural phenomenon beginning in 1963.

Source: https://thenewdaily.com.au/sport/motorsport/2023/04/22/craig-breedlove-obituary/

The vehicle went slightly above the speed of sound before it initiated the crew escape system.

Source: https://www.chiangraitimes.com/news/india-successfully-completes-crucial-test-in-gaganyaan/