Almost nothing is known of him, not even if "Saeed Alghamdi" is his real name. It is accepted that he was Saudi Arabian, and is said to have come from a town called Abha.
He arrived in the USA in June 2001 through a immigration procedure called Visa Express. Other hijackers with suspect identities used this same means to enter the US.
Prior to boarding flight 93, he shared an apartment with Ahmed Alnami in Delray Beach, Florida.