solo means nobody else on board the aircraft and specifically not one who has access to the flight controls.
maybe more precise to word it - 'nobody else on board the aircraft -
period.'
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As clever as the Monty Python people are, I doubt even they could imagine anything as wayout as the Spirit of Artifice and its novel activities.
hear the objection from the ghost of Graham Chapman , immaculately dressed army officer with swagger stick . .. . "Too silly. . .. too silly for words.."