As far as who else besides the pilots would have had the technical know how for this…..well, the authorities have also been investigating this guy:
http://www.straitstimes.com/breakin...-probe-flight-engineer-missing-mh370-20140317
Regarding the two stolen European passports, I think they did identify who those people were, who were traveling on the passports, and it was two Iranian asylum seekers. But Wikipedia notes a third phantom passenger on the plane, where the passenger manifest lists a Chinese national's passport number, yet the guy never got on the plane, and the manifest matches that passport number to someone else's name:
http://www.sify.com/news/missing-ma...-aircraft-news-international-odjuuKihbdg.html
I don't know if they ever figured out who, if anyone, got on board the plane in place of this guy.
http://www.straitstimes.com/breakin...-probe-flight-engineer-missing-mh370-20140317
Regarding the two stolen European passports, I think they did identify who those people were, who were traveling on the passports, and it was two Iranian asylum seekers. But Wikipedia notes a third phantom passenger on the plane, where the passenger manifest lists a Chinese national's passport number, yet the guy never got on the plane, and the manifest matches that passport number to someone else's name:
http://www.sify.com/news/missing-ma...-aircraft-news-international-odjuuKihbdg.html
I don't know if they ever figured out who, if anyone, got on board the plane in place of this guy.