You’d have to check the schedule for your specific dates but I think Santorini then Milos then Paros then Naxos and Athens would probably be the best order. 3 days in each sounds great. Or a small tweak: 2 days in Milos and then 4 days in Santorini (splitting time between 2 of the 4 caldera towns) or even 4 days in Paros (splitting time between Naousa and Parikia).
In 1926, Alan Cobham surveyed a flight route from the UK to Cape Town, South Africa, following this up with another proving flight to Melbourne, Australia. Other routes to British India and the Far East were also charted and demonstrated at this time. Regular services to Cairo and Basra began in 1927 and were extended to Karachi in 1929. The London-Australia service was inaugurated in 1932 with the Handley Page HP 42 airliners. Further services were opened up to Calcutta, Rangoon, Singapore, Brisbane and Hong Kong passengers departed London on 14 March 1936 following the establishment of a branch from Penang to Hong Kong.
At the same time, Juan Trippe began a crusade to create an air network that would link America to the world, and he achieved this goal through his airline, Pan American World Airways, with a fleet of flying boats that linked Los Angeles to Shanghai and Boston to London. Pan Am and Northwest Airways (which began flights to Canada in the 1920s) were the only U.S. airlines to go international before the 1940s.
Increasingly since 1978, US airlines have been reincorporated and spun off by newly created and internally led management companies, and thus becoming nothing more than operating units and subsidiaries with limited financially decisive control. Among some of these holding companies and parent companies which are relatively well known, are the UAL Corporation, along with the AMR Corporation, among a long list of airline holding companies sometime recognized worldwide. Less recognized are the private equity firms which often seize managerial, financial, and board of directors control of distressed airline companies by temporarily investing large sums of capital in air carriers, to rescheme an airlines assets into a profitable organization or liquidating an air carrier of their profitable and worthwhile routes and business operations.
Growth rates are not consistent in all regions, but countries with a de-regulated airline industry have more competition and greater pricing freedom. This results in lower fares and sometimes dramatic spurts in traffic growth. The U.S., Australia, Canada, Japan, Brazil, India and other markets exhibit this trend. The industry has been observed to be cyclical in its financial performance. Four or five years of poor earnings precede five or six years of improvement. But profitability even in the good years is generally low, in the range of 2–3% net profit after interest and tax. In times of profit, airlines lease new generations of airplanes and upgrade services in response to higher demand. Since 1980, the industry has not earned back the cost of capital during the best of times. Conversely, in bad times losses can be dramatically worse. Warren Buffett in 1999 said "the money that had been made since the dawn of aviation by all of this country's airline companies was zero. Absolutely zero."
Airlines have substantial fixed and operating costs to establish and maintain air services: labor, fuel, airplanes, engines, spares and parts, IT services and networks, airport equipment, airport handling services, booking commissions, advertising, catering, training, aviation insurance and other costs. Thus all but a small percentage of the income from ticket sales is paid out to a wide variety of external providers or internal cost centers.