is it possible that the onyesha could be based on something real there have been multiple mysterious plane crashed over the pacific ocean and only some of them have been solved i know that it sounds craze maybe it is but i am so convinced that it may be

Certain parts of Lost are based on other mythologies and conspiracies, so some of it is grounded in "truth". For example, wewe could easily say that Amelia Earhart whose plane famously went missing, ended up on The Island and she is in fact Amelia from New Otherton, Juliet's book club friend.