What is a flight certificate?
I wondered that too. Was a “flight certificate” permission to fly to the US or was it some kind of certification of his flying abilities from the Saudis? This is the hijacker who didn’t make it onto the flight, btw, and his documents were found buried somewhere (where?), so obviously he thought it was pretty incriminating.
But as livius point out, maybe it is something else. Another question I had was how they found a cache of documents that had been buried.