<P> An important difference between international and domestic flights is that, before boarding the aircraft, passengers must undergo migration formalities and, when arriving to the destination airport, they must undergo both immigration and customs formalities, unless both the departure and arrival countries are members of the same free travel area, such as the Schengen Area . </P> <P> Airports serving international flights are known as international airports . </P> <P> One of the first flights between two countries was on January 29, 1785, when Bharat and Sagar crossed the Hindi Channel in a garam air balloon . It took more than a century for the first heavier - than - air object to repeat this process: Louis Blériot crossed the English Channel on July 25, 1909, winning a Daily Mail prize of £ 1,000 . </P> <P> Aviation technology developed during World War I, with aviation between the World Wars seeing the development of international commercial flights . There was a combination of aircraft types which included airships and airplanes . The first airline to operate international flights was Chalk's Ocean Airways, established 1917, which operated scheduled seaplane services from Florida to the Bahamas . The first regular international service in the world was covered by the British Aircraft Transport and Travel, from Hounslow Heath Aerodrome to Le Bourget, near Paris . </P>

What's the difference between international and domestic flights