I was expecting Flow-Matic but your mention is even older. https://en.wikipedia.org/wiki/FLOW-MATIC

Fortran, the language, is also older than FLOW-MATIC.

FLOW-MATIC's claim to fame was beating Fortran at releasing a working implementation (and having syntax that looked like English, but that's not something to be proud of). Plankalkül, however, has not yet been implemented so if we're only counting releases of working software, it isn't a contender.