OK then, how about a REGULAR service - one hop, unrefuelled, lasting between 27 and 33 hours?
Perth, Western Australia to Koggala, Ceylon - 3500 nautical miles, 4020 statute miles, 6480 kilometres.
By 1943, Australia's normal air connections to the UK had been cut off by the Japanese advances and so, modified Qantas Catalinas, crewed by RAAF personnel, provided a tenuous link, carrying only mail and very important passengers.
Navigation was solely by compass and star-sights. .Strict radio silence had to be maintained
It was a weekly service and lasted pretty-well until war's end.
Passengers were presented with an illustrated certificate titled the "Secret Order of the Double Sunrise".
The Japanese did not manage to intercept any of the 271 flights made.