Definition
Variants of a single-seat military aircraft that have been modified to include a second seat, typically used for pilot instruction, conversion training, or check rides on that specific aircraft type.
Plain English
A version of an aircraft that normally carries only one pilot but has been built with a second seat so an instructor can fly along and teach a student how to operate that aircraft.
Context Anchor
Seen in discussions of training aircraft, simulators, and electronic learning tools that let an instructor guide or monitor a learner.
Why Pilots Care
Some aircraft — particularly fighters and certain warbirds — exist only as single-seat designs in their operational form. Without a two-seat training version (or a high-fidelity simulator), there is no practical way for an instructor to fly with a student during initial conversion onto the type.
Intuition Check
Do not read this as any airplane or device that simply has two seats. In this context, it means a version intended for training, with room or controls arranged so an instructor and learner can work together.
Example Sentence 1
Because the F-16 is a single-seat fighter, new pilots transition onto the type using two-seat training versions before flying solo.
Example Sentence 2
E-learning scenarios often model procedures from two-seat training versions to show how an instructor would intervene during a student’s first solo practice.