Nine weeks in Greece is a dream itinerary it certainly gives you lots of flexibility. As you seem to have Athens and the Peloponnese sorted, you just need to sort out your five weeks on the islands. What you need to realize, however, is that the islands are not all mutually interconnected, but rather they are ‘grouped’ – both administratively and from the point of view of transport routes. Here are the main groups.
In the 1990s, "open skies" agreements became more common. These agreements take many of these regulatory powers from state governments and open up international routes to further competition. Open skies agreements have met some criticism, particularly within the European Union, whose airlines would be at a comparative disadvantage with the United States' because of cabotage restrictions.
Despite continuing efficiency improvements from the major aircraft manufacturers, the expanding demand for global air travel has resulted in growing greenhouse gas (GHG) emissions. Currently, the aviation sector, including US domestic and global international travel, make approximately 1.6 percent of global anthropogenic GHG emissions per annum. North America accounts for nearly 40 percent of the world's GHG emissions from aviation fuel use.
Since airline reservation requests are often made by city-pair (such as "show me flights from Chicago to Düsseldorf"), an airline that can codeshare with another airline for a variety of routes might be able to be listed as indeed offering a Chicago–Düsseldorf flight. The passenger is advised however, that airline no. 1 operates the flight from say Chicago to Amsterdam, and airline no. 2 operates the continuing flight (on a different airplane, sometimes from another terminal) to Düsseldorf. Thus the primary rationale for code sharing is to expand one's service offerings in city-pair terms to increase sales.