"No code word is believed to have been used."
Huh?...
Athens, Greece has always been a soft underbelly of air traffic....
"No code word was used". This I believe means that the caller was not thought to be from a major terrorist group. All the major groups have established a "code word" with news agencies and possibly law enforcement units as well.
The secret pass word, nee "code word", establishes the authenticity of the information given to the news/law enforcement agency.