Source:  Elines

Unexpected aircraft changes present questions as to how Flight Attendants are to determine their proper work positions.  Our JCBA provides the language for these instances in Section 7.Q.7: 

In the event of an equipment change where the new equipment does not require the original number of Flight Attendants scheduled, scheduling will first reassign Reserves, if any.  If the trip still does not require the remaining number of Flight Attendants, the senior bid Lineholder(s) may fly or opt off the pairing. 

However, Language Qualified (LQ) Flight Attendants and the International Purser; Flight Attendants with special qualifications may be required to take and/or complete the pairing where their special qualification(s) are still required. If the pairing does not require the original number of LQ Flight Attendants, the senior LQ Flight Attendant may opt off the trip. 

If the Reserve is not reassigned and travels on the same flight, she/he will be included in the senior option as provided in Section 7.O. of our JCBA. 

The surplus Flight Attendant(s), who have either been removed or who opt off the pairing shall, at her/his option, be pay protected in accordance with the provisions of Section 7.Q.7. of our JCBA.

Additionally, unassigned positions are identified and filed at the beginning of the flight, after Flight Attendant boarding time and before pre-flight duties begin. This will primarily occur during briefing with any unassigned positions filled in seniority order among the Members of the working crew.

If there are multiple base pairings assigned to a flight, the base pairing that was originally assigned to the flight will work their positions and the remaining positions are filled by seniority.