It's an age-old question for most F/As wanting to have some control over their schedule: “Why aren't unlimited trip trades with open flying permitted?”

I've asked it a million times myself, usually when staring at the Unimatic terminal, wanting to toss it (and the busted printer) out on to the tarmac.

United today offers their answer as to why unlimited trip trades with open flying are not permitted.  The following excerpt is from an article that appears in their Aug 18 Onboard Updates:

Many flight attendants responding to the Flight Attendant Scheduling and Support (FASS) survey on SkyNet have asked, “Why aren't unlimited trip trades with open flying permitted?”

The simple response is: reserve coverage. In conjunction with the AFA, Scheduling creates reserve patterns to meet the demand of potential open trips throughout the month.

Since reserves are available only 19-20 days per month, those days are strategically placed to best meet the projected demand for open trips and support the operation.

Historically, weekends (Friday through Monday) are the most popular days out of which to trade. Since reserves are a limited resource, it is not possible to have all reserves available every weekend without further reducing coverage mid-week and at the beginning and end of the month. Those are the times when reserve utilization is high.

Scheduling plans for high reserve availability at the beginning of the month due to month-end legality drops and also at the end of the month because high-time reserves are unable to fly. Although it might seem that by trading out of a weekend, there would be fewer mid-week trips for reserves to fly, that's not the case. There is still an operational need to maintain a minimum level of reserve availability to cover no-shows, last-minute sick calls, illegalities, misconnects and irregular operations.

Although some other carriers may offer unlimited trip trades, their contracts allow them the flexibility to move reserve days to accommodate their liability and react to shortages. Our Agreement does not permit this, so it is not operationally feasible to offer unlimited trip trades with open flying.

However, the daily trip trade allocations at all locations have been increased from three to four percent, per the new Agreement. It also is important to note that recent flight attendant furloughs and retirements have reduced domicile populations and affected the number of available allocations. For example, a domicile with 800 active flight attendants would have 24 slots at three percent. That same domicile, reduced to 500 flight attendants, would have only 20 slots, despite the increase to four percent.