Starting February 14th and for about six months, the airport express bus service linking the Ethniki Amyna station and the airport will be suspended. For details read this article in the Kathimerini.
Too bad for the inconvenience because this is by far the quickest way plus the cheapest way combined for anyone to travel from airport to downtown ( airport express bus to Ethniki Amyna, a station in the Metro blue line, then Metro blue line to Syntagma station will cost just 80 cents more, Syntagma is the parliament station downtown. ) The other airport express buses are not so express because they go through the traffic of Athens' streets, whereas the above mentioned way cuts the traffic delay on streets by travelling on the Metro Subway, and the Metro ticket costs as little as 80 Euro cents. Paying an additional 80 Euro cents for the Metro subway is nothing considering time is money.