What advancements allowed for longer flights in aircraft in 1919?

In 1919, the advancements that significantly contributed to longer flights in aircraft primarily revolved around stronger and more reliable engines. During this period, aviation technology was evolving rapidly, and improvements in engine design and manufacturing were vital. These engines became capable of generating more power while remaining lightweight and efficient, which allowed aircraft to fly longer distances without needing frequent refueling stops.

The development of more reliable engines also meant that pilots could have greater confidence in their aircraft, leading to longer and more predictable flight operations. Innovations such as better fuel types, enhanced cooling systems, and improved materials for engine construction played crucial roles in extending flight range. This technological progress laid the groundwork for future developments in commercial and military aviation, setting the stage for the boom in air travel that would follow in the coming decades.

While the other options touch on important aspects of aviation, such as marketing, passenger comfort, and navigational technology, they do not directly address the foundational changes in aircraft capability that resulted in the ability to sustain longer flights during that specific time.