What characteristic defines a "line holder" in the aviation industry?

A "line holder" in the aviation industry is defined by being awarded a specific line of time, which refers to a series of scheduled flights or trips that they operate during a particular period. This designation indicates that the flight attendant has seniority and has been given regular flying assignments based on their availability and preferences.

Unlike reserve flight attendants, who may be called in to cover flights on short notice and typically have a more flexible schedule, a line holder has a set schedule that they work for that month. This pattern not only allows for more predictability in their work-life balance but also enables them to plan for personal commitments accordingly.

The other options relate to aspects of a flight attendant's role but do not specifically pertain to the definition of a line holder. Flexibility in scheduling pertains more to reserve employees, while technical duties are focused on operational tasks rather than scheduling status. Similarly, the management of passenger services, while critical to the role of a flight attendant, does not define the specific status of being a line holder.