fortuitous

Happening by chance; coincidental, accidental.

[…] and during the ten days of their stay at Hartfield it was not to be expected—she did not herself expect—that any thing beyond occasional, fortuitous assistance could be afforded by her to the lovers.

‘It is not for one, situated, through his original errors and a fortuitous combination of unpropitious events, as is the foundered Bark (if he may be allowed to assume so maritime a denomination), who now takes up the pen to address you—it is not, I repeat, for one so circumstanced, to adopt the language of compliment, or of congratulation. That he leaves to abler and to purer hands.

Happening by a lucky chance; lucky or fortunate.

And then he met John Dowsett, the great John Dowsett. The whole thing was fortuitous. This cannot be doubted.

Admiral Kurita has no identification charts for escort carriers, and, so, assumes that the distant targets are fleet carriers. Commensurately, by scale, their escorts must either be battleships or cruisers. The Japanese forces therefore continue to load armor-piercing rounds, what will turn out to be a very fortuitous mistake for their targets for as long as it lasts.

Happening independently of human will.