This historical Australian newspaper article contains the keyword "airplane": 25 Jul 1925, "DURALUMIN. THE WONDER METAL.":
http://nla.gov.au/nla.news-article270305542
DURALUMIN. - THE WONDER METAL. - The Woodend Star (Vic. : 1888 - 1942) - 25 Jul 1925
In duralumin, the new metal invented especially for aircraft, lies the secret of the far-flying exploits of the giant dirigibles. Trans-Atlantic flying ...
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