Which airfield configuration is considered the least flexible?

The configuration that is considered the least flexible is a single runway. This is primarily because a single runway can only accommodate one aircraft at a time for both takeoffs and landings. This limitation directly impacts the airport's ability to manage traffic, resulting in increased wait times and reduced efficiency, especially during peak traffic periods.

In contrast, a dual runway or multi-runway system allows for simultaneous operations, which significantly enhances an airfield's capacity to handle multiple aircraft efficiently. A parallel taxiway also adds flexibility by allowing aircraft to move to and from the runway without interfering with takeoff and landing operations. Hence, the single runway configuration is inherently limited in its operational flexibility, making it less adaptable to varying traffic demands and conditions.