An entire day... or just over....

This is from memory... so without question it won't be entirely accurate.

It's a complex story. Lot of a design issues (tanks for fuel), and politics... where they could land for refueling. I believe the first passenger flights, (very late 30's if memory serves) flew to the Azores, onto Spain, and eventually France. They had sleeping compartments.

Not sure when the northern route began... which meant a stop in Iceland. I do remember Britain refused to allow them to land at first for 'competition' reasons.