Having a large number of aircrew on PAS PES or FTCA is one thing, they can opt out of service at any time. The FRI guarantees service for the period stated, this allows for manning plots to be managed better, knowing when individuals can leave, might leave, can't leave. The benefits of this can be seen at Apachemanning.com or B!
FRIs are contentious, but for the treasury it is exceptional value for money.
