Disappearing planes, and no clear answers, just isn’t something that happens in aviation. There hadn’t been a single commercial aircraft go missing in the prior 13 years. Nearly all the aircraft that have disappeared have been probable crashes. Perhaps surprisingly commercial planes simply aren’t ever stolen. At least they almost never are.
Yet a Boeing 727 disappeared on May 25, 2003 from the international airport in Luanda, Angola. The plane used to belong to American Airlines. It was never found.