nominal

[Matthew Gordon]

In the coverage of the space shuttle tragedy I've been struck by the use
of 'nominal' as an apparent synonym for 'normal'. A reporter had
mentioned it as a special usage, and in a press conference NASA people
spoke of a mission to take a "nominal load of supplies" to the space
station and later of sensors reading an "off-nominal" event.

Is this usage just a NASAism or does it have broader currency in
aviation or maybe military usage?