What is the primary use of propeller aircraft?

The primary use of propeller aircraft is largely centered around their efficiency and cost-effectiveness for shorter distances, making them particularly suitable for European short-haul and domestic routes. Propeller aircraft are generally lighter and can operate on shorter runways compared to jet aircraft, which makes them advantageous for regional flights that do not demand the speed or range of jets. This adaptability allows them to serve smaller airports that are common in Europe and other regions, providing connectivity between cities where demand for air travel is moderate.

In contrast, the other options involve contexts where propeller aircraft are less suitable. International long-haul flights typically benefit from the higher speeds and altitudes that jet aircraft offer, as do cargo operations over oceans where time efficiency is critical. Military operations often employ fast jets and larger transport aircraft to meet tactical and strategic needs in combat situations. Thus, propeller aircraft excel in regional travel, supporting the idea that they are primarily used for short-haul and domestic routes.