What features defined modern airliners in the 1930s?

Modern airliners in the 1930s were characterized by significant advancements in design and technology that transformed air travel. The defining features included being primarily two-engine designs, which allowed for improved reliability and performance. The use of all metal construction was also significant, marking a departure from earlier aircraft that often used wood and fabric, leading to enhanced strength and durability.

Additionally, the emphasis on passenger seating catered to the growing demand for commercial air travel, allowing airlines to transport a larger number of passengers over longer distances. These developments not only enhanced the passenger experience but also paved the way for the expansion of commercial aviation as a viable and popular mode of transportation during that era.

In contrast, other options reflect characteristics that do not align with the historical context of the 1930s. For instance, high-capacity seating paired with turbo engines would not accurately describe airliners of that time, as turbo engines became more common in later decades, and high-capacity models were not as prevalent. Similarly, single-engine designs with fabric wings do not reflect the sophistication of commercial aircraft in the 1930s, nor did medium-range jet capabilities, as jets were not introduced until the late 1940s and 1950s.