It seems you would not lose that much time going by ship or plane, and in a lot more comfort. When I was a kid in the 50s, I took DC-3s Green Bay to Chicago a few times. IIRC, we made three stops along the way and it was not unusual to get stuck due to weather in some tank town along the way. The railroad line, the Flying 400 could make the trip in a little over three hours with no rain delay. The DC-3s were noisy. However, I once went on a Ford Trimotor on an excursion, and sat next to the wing engine. It amazes me that commercial aviation made any headway at all pre turbine powered pressurized aircraft.In the Netherlands they worked also on Long range Airliner
to get to there colony in Indonesia
like Fokker Ontwerp 160 to 180 the "Intercontinental"
Why were increased demand for long range Airliner end of 1930s ?
One reason was economic and faster travel time:
Let's take SABENA route Brussel to Leopoldville in Belgium Congo in begin 1930s
with Savoia Marchetti S.73
Day 1: Brussel -> Marseille flight over Mediterranean Sea, landing at Oran (Algeria)
Day 2: Oran -> Colomb Bechar -> Reggane
Day 3: Reggane-> Gao -> Niamey
Day 4: Niamey -> Zinder -> Fort-Lamy
Day 5: Fort-Lamy -> Fort Archambault -> Bangui -> Cuquilhatville
Day 6: Cuquilhatville -> Leopoldville.
6 days with 12 stop to refuel with 5 overnight stay and servicing the Aircraft
you notice the logistic nightmare to bring petrol & spare parts in middle of nowhere...
With Fokker "Intercontinental" range Amsterdam -> New York
Would reduce SABENA flight time to two days with one overnight stay at Reggane
This reduce logistic need only to Reggane - not 12 stations across Africa.