Hydra is great but it does take a bit of time and effort to get to from the Cyclades. You’ll need to ferry to Athens, then might have to overnight there, then ferry to Hydra. Whereas Naxos, Paros, Milos, Folegandros, etc. would all be one direct ferry from Santorini or Mykonos. If you do go to Hydra then Leto Hotel is a great choice close to the port and shops and restaurants.
Service during the early 1920s was sporadic: most airlines at the time were focused on carrying bags of mail. In 1925, however, the Ford Motor Company bought out the Stout Aircraft Company and began construction of the all-metal Ford Trimotor, which became the first successful American airliner. With a 12-passenger capacity, the Trimotor made passenger service potentially profitable.[29] Air service was seen as a supplement to rail service in the American transportation network. 

My boyfriend and I will be traveling to Greece on August 1-11th. We have 10 days. Is this a feasible itinerary for a couple in their early 30s who want beach, relaxation, good food, boating, and some history? Fly into Athens have one full day there then fly to Naxos for a day and a half, Milos for 3 nights, then Santorini for 3 nights, then back to Athens for our flight? We chose Milos over Naxos at first, but after reading your blog it seems the beaches in Naxos may be better?

Codesharing is the most common type of airline partnership; it involves one airline selling tickets for another airline's flights under its own airline code. An early example of this was Japan Airlines' (JAL) codesharing partnership with Aeroflot in the 1960s on Tokyo–Moscow flights; Aeroflot operated the flights using Aeroflot aircraft, but JAL sold tickets for the flights as if they were JAL flights. This practice allows airlines to expand their operations, at least on paper, into parts of the world where they cannot afford to establish bases or purchase aircraft. Another example was the Austrian–Sabena partnership on the Vienna–Brussels–New York/JFK route during the late '60s, using a Sabena Boeing 707 with Austrian livery.
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.
Domestic air transport grew in China at 15.5 percent annually from 2001 to 2006. The rate of air travel globally increased at 3.7 percent per year over the same time. In the EU greenhouse gas emissions from aviation increased by 87% between 1990 and 2006.[75] However it must be compared with the flights increase, only in UK, between 1990 and 2006 terminal passengers increased from 100 000 thousands to 250 000 thousands.,[76] according to AEA reports every year, 750 million passengers travel by European airlines, which also share 40% of merchandise value in and out of Europe.[77] Without even pressure from "green activists", targeting lower ticket prices, generally, airlines do what is possible to cut the fuel consumption (and gas emissions connected therewith). Further, according to some reports, it can be concluded that the last piston-powered aircraft were as fuel-efficient as the average jet in 2005.[78]
In many ways, the biggest winner in the deregulated environment was the air passenger. Although not exclusively attributable to deregulation, indeed the U.S. witnessed an explosive growth in demand for air travel. Many millions who had never or rarely flown before became regular fliers, even joining frequent flyer loyalty programs and receiving free flights and other benefits from their flying. New services and higher frequencies meant that business fliers could fly to another city, do business, and return the same day, from almost any point in the country. Air travel's advantages put long distance intercity railroad travel and bus lines under pressure, with most of the latter having withered away, whilst the former is still protected under nationalization through the continuing existence of Amtrak.
Excellent choice of islands, though getting between them presents one or two challenges (they are not as conveniently connected like the Cycladic or Dodecanese islands so island hopping is not as popular in this island group). All three islands are served by airports with year-round connections to Athens and in the Summer with international charter flights from Europe. Let’s take the pros and cons of each island.