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.
The Dutch airline KLM made its first flight in 1920, and is the oldest continuously operating airline in the world. Established by aviator Albert Plesman, it was immediately awarded a "Royal" predicate from Queen Wilhelmina. Its first flight was from Croydon Airport, London to Amsterdam, using a leased Aircraft Transport and Travel DH-16, and carrying two British journalists and a number of newspapers. In 1921, KLM started scheduled services.
Also, if there are any other suggestions you have in general for Athens and Santorini I would love to hear them. I would like to be able to leave Athens early morning on Day 3 so that we can have almost a full day on our first island. We would like to see as much as we can without feeling like we are running around from island to island the whole time.
Like Imperial Airways, Air France and KLM's early growth depended heavily on the needs to service links with far-flung colonial possessions (North Africa and Indochina for the French and the East Indies for the Dutch). France began an air mail service to Morocco in 1919 that was bought out in 1927, renamed Aéropostale, and injected with capital to become a major international carrier. In 1933, Aéropostale went bankrupt, was nationalized and merged into Air France.
Although Germany lacked colonies, it also began expanding its services globally. In 1931, the airship Graf Zeppelin began offering regular scheduled passenger service between Germany and South America, usually every two weeks, which continued until 1937. In 1936, the airship Hindenburg entered passenger service and successfully crossed the Atlantic 36 times before crashing at Lakehurst, New Jersey, on May 6, 1937. In 1938, a weekly air service from Berlin to Kabul, Afghanistan, started operating.
A complicating factor is that of origin-destination control ("O&D control"). Someone purchasing a ticket from Melbourne to Sydney (as an example) for A$200 is competing with someone else who wants to fly Melbourne to Los Angeles through Sydney on the same flight, and who is willing to pay A$1400. Should the airline prefer the $1400 passenger, or the $200 passenger plus a possible Sydney-Los Angeles passenger willing to pay $1300? Airlines have to make hundreds of thousands of similar pricing decisions daily.