The act of exiting or getting off an airplane; present participle of deplane.
From 'deplane' + '-ing' (gerund/present participle suffix). This form emerged in aviation industry terminology as airplanes became common in the mid-20th century.
You'll hear 'deplaning procedures' announced on every flight, which sounds professional but is basically just a fancy way of saying 'getting off the plane in an organized way.'
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