Then let us compute the currency requirements.

A pilot cannot fly over 1000 hours per year:
http://www.risingup.com/fars/info/part121-503-FAR.shtml

Which means 250 hours in 3 months on average.

With 16 hour legs, it means 15 flights in 3 months.

Between a crew of 4, each of them needs 3 landings in 90 days: 12 total in 90 days.

But a 4 pilot crew cannot possibly fly over 16 hours. I cannot find flight time restrictions for a crew of 5 pilots.

We are diverging far from the original topic, but hey….what the heck.

Getting enough landings for long haul crews is actually a very complex topic, and one that has been the subject of considerable conversation for the last few years. A bit of history: One fine day approximately 10-12 years ago, a heavily loaded UAL 747 departed KSFO and experienced an engine failure very shortly after takeoff. The Pilot Flying(PF) was a relief First Officer and he did not fly the airplane properly. In short, he corrected for the yaw with aileron instead of rudder, which is a big no-no (it causes the flight spoilers to deploy). The airplane’s climb performance was severely restricted due to heavy weight and the poor manipulation of the flying controls. The airplane almost hit San Bruno Mountain. http://en.wikipedia.org/wiki/San_Bruno_Mountain

In the subsequent investigation, it became apparent that the subject First Officer had not conducted an actual (non simulator) takeoff in a B747 in almost three (3) years! UAL researched their pilot qualification database and found that as many as 50 were in a similar situation, with the record holder being eight (8!!) years. It seems that there is a pilot subculture that finds relief flying appealing and purposely bid it. In a normal rotation, the “A” Captain gets first choice on takeoff/landing, then the “A” FO, then the “B” Captain, and finally, the lowly relief “B” FO. Turns out there are almost no landings or takeoffs left over for them. The problem is exacerbated when particular pilots fly only very long flights all the time (correspondingly fewer takeoffs/landings).

It was also found in the ensuing investigation this type of engine failure (it was accompanied by high vibration) was not easy to reproduce in a simulator, and furthermore, when attempted, was very damaging to the simulator! One other quick hit: how much attention should be given to the whole topic given the increasingly remote chance of engine failure due to the engines getting more and more reliable?

Airlines scrambled to amend their requirements in the wake of this incident. Some chose to make their pilots go back to the simulator more often. Others worked with their unions to include some short hops in more rotations. (This was problematic becuase there are only a limited number of short haul wide body trips). Others chose to start counting very closely the number of tkofs/ldgs that individuals had recently, and required the “a” crews to give up some to a relief crew member when necessary.

Long story short, this is a very complex topic, but I hope I have illustrated how complex seemingly simple issues can become for operators (airlines). Often, the manufacturers (both A and B) seem to overlook these in their glowing press releases about the capabilties of their wonderful new birds.

One final point: The UAL incident clearly illustrates that simply adding more pilots does not necessarily increase safety, a point apparently lost on the “5 pilot crowd” in the unions at the carriers that are doing Ultra Long Haul Flying.

Final final point: Sometimes, wedging in a short flight for a long haul airplane can be very productive. For example, lets say a 777 comes into ATL and is scheduled to be down for 8 hours prior to it’s next long haul flight. A round trip to KMCO can easily be accomplished in less than half that time. Doing so generates additional revenue (getting more revenue out of the airframe), provides a lot of seats to a popular vacaction destination, and facilitates pilot training/qualification. Thus, Singapore may have “other” reasons for relative short haul, apparently un-economic flying for their A340-500’s.