Here's a little more info on "aircheck" from this web site:
> ... AIRCHECK
> * According to some reports, the oldest existing aircheck dates to
> the Armistice Day broadcast, November 10, 1923.
> * Some WEAF broadcasts of the NY Philharmonic are said to predate
> that slightly.
Tom Fine wrote:
> What is the genesis of the term "aircheck" and how did it come to mean
> "off-air recording", or did it mean something different at another time?
> -- Tom Fine