the psychic
In Claire’s original flashbacks, the psychic she visited went into a panic and made it clear that she needed to raise Aaron herself or obviously something awful would occur. We of course never learned what he saw. He then “fooled” her into thinking he had a couple lined up for the adoption in LA telling her what flight to take (gave her ticket) when in reality he apparently knew the plane was going to crash and Claire would therefore not be able to give Aaron away. Does anyone have any thoughts on why it would be vital for Claire to raise Aaron and his significance?

The psychic (Richard Malkin) admitted to Eko in a later episode that he is a fraud. Someone must have made him tell Claire all these things. Considering that Richard’s daughter was miraculously resurrected after drowning, we might guess that Jacob had something to do with it.
Probably Jacob made a deal with him in order to make sure things happened correctly. In exchange for that deal he resurrected his daughter maybe…