Which formation is considered the least secure flying and landing formation?

The trail formation is considered the least secure flying and landing formation primarily due to its structural vulnerability and risk of collisions. In a trail formation, all aircraft are lined up directly behind one another, which can create significant challenges during landing, takeoff, and navigation. This arrangement limits visibility and situational awareness for the aircraft in the trail position, making it difficult to observe and respond to potential threats or changes in the environment.

Additionally, if the lead aircraft encounters a problem, the trailing aircraft lack the ability to maneuver effectively to avoid obstacles or danger. This tight coupling can lead to increased risk during operations, particularly in environments where enemy action or adverse weather is a factor. In contrast, other formations, such as diamond, line, or wedge, allow for greater dispersion, improved visibility among aircraft, and better tactical options, enhancing overall operational security.