hey there,

Normally airline assigns the 12 hours to 14 hours of shifts. Sometimes it could be increased if you are on an international long route flight.

Flight attendants may be away from home for several days in a row including weekends and holidays and therefore must be flexible. The maximum number of flying hours per day is set by union agreement, and on-duty time is usually limited to 12 hours per day, with a daily maximum of 14 hours.

hope this will help you