Definition
On flight crews that include a supplemental pilot (a third pilot carried on long-haul operations to provide rest relief), the supplemental pilot is qualified and authorized to occupy either the pilot-in-command seat or the second-in-command seat during the cruise portion of flight, allowing one of the primary pilots to take a scheduled rest break. The supplemental pilot does not perform takeoff or landing duties.
Plain English
On long flights with three pilots, the extra pilot is trained and allowed to sit in either the captain's seat or the first officer's seat so one of the regular pilots can rest during cruise.
Context Anchor
Seen in crew scheduling, long-flight crew planning, and rules about pilot rest and relief during flight.
Derivation
Supplemental comes from the Latin supplementum, meaning something added to make up a shortfall. Here it describes a pilot added to the crew to make up for the rest the primary pilots need on long flights.
Why Pilots Care
Provides operational flexibility for crew rest and seat-specific experience without requiring a full crew change.
Grounding Statement
Picture a long flight where one required pilot leaves the flight deck for an approved rest period; the supplemental pilot is the qualified pilot who fills that role.
Intuition Check
Do not read “supplemental” as “optional” or “less qualified.” Here it means an additional pilot carried to support the crew, and that pilot still must meet the requirements for the position being assumed.
Example Sentence 1
Because the flight was scheduled for fourteen hours, the airline assigned a supplemental pilot who could assume either of these positions during the cruise rest rotation.
Example Sentence 2
For the overnight ferry flight the supplemental pilot can assume either of these positions to share the workload.