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Aviation Terminology 101: The Language of Crew Optimization

To successfully develop rules and optimization models in the aviation industry, you must first speak the language of the domain. Airline crew scheduling is built upon a rigid, standardized vocabulary that describes time, geographical movement, and crew member states.

The Jeppesen Rave language and CARMEN optimization engine map directly to these domain concepts. Understanding this terminology is the absolute prerequisite for any Rave Developer.

1. The Operational Hierarchy

Crew schedules are constructed using a strict building-block hierarchy.

graph TD
    Leg["Leg (Sector)<br>A single flight from Airport A to Airport B"]
    Duty["Duty (Working Day)<br>A sequence of legs + ground duties"]
    Pairing["Pairing (Trip)<br>A sequence of duties starting & ending at base"]
    Roster["Roster (Plan)<br>A month-long schedule for a named crew member"]

    Leg --> Duty
    Duty --> Pairing
    Pairing --> Roster

  • Leg (or Sector): An individual flight from an origin airport to a destination airport. This is the smallest indivisible unit of work in crew scheduling.

  • Duty (or Duty Period): A sequence of flights flown by a crew in a single working day. It begins when a crew member reports for work and ends when they are released into a legal rest period.

  • Pairing (or Trip): A sequence of consecutive flight legs (grouped into duties) that starts from and ends at the base airport of the airline company, flown by a single anonymous crew.

  • Roster (or Plan): The final schedule assigned to a specific, named crew member over a defined planning horizon (typically a month).

2. Core Time & Pay Concepts

  • Block Time: The total time from the moment an aircraft pushes back from the departure gate (blocks removed) until it parks at the arrival gate (blocks inserted). Crew pay is often heavily tied to block time.
  • Flight Time: The time the aircraft is actually in the air (wheels up to wheels down).
  • Briefing / Debriefing (Report / Release): The mandatory time a crew member must be present before a flight (briefing) and the time required after a flight to complete post-flight duties (debriefing).
  • TAFB (Time Away From Base): The total elapsed time from the moment a crew member reports for their pairing at their home base until they are released at their home base at the end of the trip. Many union contracts guarantee minimum pay based on a fraction of TAFB.

3. Crew States & Logistics

  • Deadheading: Transporting crew members on flights as passengers rather than as operating crew. This is often required to position a crew member to a different airport to operate a subsequent flight, or to return them to their base.

  • Sit Time (or Connection Time): The ground time between two consecutive operating flights within the same duty period.

  • Layover (or Night Stop): The rest period between two duty periods where the crew sleeps at a hotel in a non-base city.

  • Base Airport: The home airport where a crew member is permanently stationed. All pairings must originate and terminate here.