As a starter to explore ferry services, go to the and punch in your route searches. Note: air travel between islands is not generally good. Air travel is normally only feasible between Athens (or other mainland destinations) and the island in question. Some exceptions do exist – Rhodes Kastellorizo, Kos-Leros-Astypalaia, Thessaloniki-Limnos-Ikaria etc. but again you will need bookings weeks in advance.

Considering your interests (great food, hiking, beaches, nightlife unimportant) then Naxos should definitely be your other island. (And Naxos has many daily ferry connections with both Santorini and Athens.) Also, Athens needs at least one full day to explore so you should drop any thoughts about Delphi or Nafplio. Also, I would look into flights from Athens to Santorini on your night of arrival. If you could get to Santorini that night (and move your day in Athens to the end of your trip) you’d almost gain an entire day and could spend two nights on Naxos.
Yes, it’s possible. Get the SeaJet ferry from Athens to Mykonos. It should arrive at 9:30am or shortly after. You’ll have to hurry to store you’re luggage at the Sea and Sky travel agency across from the Old Port and then buy tickets for Delos. The last ferry to Delos leaves at 11am or maybe 11:30am. Ferry to Delos is about 30 minutes. Last ferry back is at 3pm which will give you plenty of time before the last ferry of the day to Naxos (at 6:15pm on SeaJet). All the ferries mention here use the Old Port. Don’t book any ferries that use the New Port or you’ll have trouble making the connections.
The next big boost for the airlines would come in the 1970s, when the Boeing 747, McDonnell Douglas DC-10, and Lockheed L-1011 inaugurated widebody ("jumbo jet") service, which is still the standard in international travel.[35] The Tupolev Tu-144 and its Western counterpart, Concorde, made supersonic travel a reality.[36] Concorde first flew in 1969 and operated through 2003. In 1972, Airbus began producing Europe's most commercially successful line of airliners to date. The added efficiencies for these aircraft were often not in speed, but in passenger capacity, payload, and range. Airbus also features modern electronic cockpits that were common across their aircraft to enable pilots to fly multiple models with minimal cross-training.
The almighty church has kept nightlife in check. If you must see and be seen, head to quietly glamorous Astivi or Stoa bar, on miniature Agia Lesvias square, in Hora. Beach life is generally languid and low-key; Psili Ammos and Livadi Geranou are our favourite hideouts. Dinner reservations are essential at Benetos, for Med-Asian fusion on an organic farm, and Lambi for grilled fish on a purple pebble beach.
By the end of the 1930s Aeroflot had become the world's largest airline, employing more than 4,000 pilots and 60,000 other service personnel and operating around 3,000 aircraft (of which 75% were considered obsolete by its own standards). During the Soviet era Aeroflot was synonymous with Russian civil aviation, as it was the only air carrier. It became the first airline in the world to operate sustained regular jet services on 15 September 1956 with the Tupolev Tu-104.
A more recent development is the airline alliance, which became prevalent in the late 1990s. These alliances can act as virtual mergers to get around government restrictions. Alliances of airlines such as Star Alliance, Oneworld, and SkyTeam coordinate their passenger service programs (such as lounges and frequent-flyer programs), offer special interline tickets, and often engage in extensive codesharing (sometimes systemwide). These are increasingly integrated business combinations—sometimes including cross-equity arrangements—in which products, service standards, schedules, and airport facilities are standardized and combined for higher efficiency. One of the first airlines to start an alliance with another airline was KLM, who partnered with Northwest Airlines. Both airlines later entered the SkyTeam alliance after the fusion of KLM and Air France in 2004.
Ferries are not really cheap any more – certainly not like they used to be – but the vessel fleet is better, safer and faster than in previous years so the cost is justified. You can get exceptionally cheap deals on longer-haul routes if you are prepared to forego a booked seat: €14 v €40 on a run to a mid-distant island, but it’s probably wise to consider taking fast catamarans to get to core islands (Mykonos, Santorini, Paros etc.) and even then, go the extra 10/15% for Business or even VIP class for the extra comfort. On longer hauls it can be cheaper to fly if you seek out flights online and book beforehand.
Major airlines dominated their routes through aggressive pricing and additional capacity offerings, often swamping new start-ups. In the place of high barriers to entry imposed by regulation, the major airlines implemented an equally high barrier called loss leader pricing.[38] In this strategy an already established and dominant airline stomps out its competition by lowering airfares on specific routes, below the cost of operating on it, choking out any chance a start-up airline may have. The industry side effect is an overall drop in revenue and service quality.[39] Since deregulation in 1978 the average domestic ticket price has dropped by 40%.[40] So has airline employee pay. By incurring massive losses, the airlines of the USA now rely upon a scourge of cyclical Chapter 11 bankruptcy proceedings to continue doing business.[41] America West Airlines (which has since merged with US Airways) remained a significant survivor from this new entrant era, as dozens, even hundreds, have gone under.