Flight Planning - Filing Suboptimal Plans

Filing Suboptimal Plans

Despite all the effort taken to optimise flight plans there are certain circumstances where it is advantageous to file suboptimal plans. In busy airspace with a number of competing aircraft, the optimum routes and preferred altitudes may well be oversubscribed. This problem can be made worse by busy periods, for example where everyone wants to arrive at an airport as soon as it opens for the day. If all the aircraft file an optimal flight plan then to avoid overloading, air traffic control may refuse permission for some of the flight plans or delay the allocated takeoff slots. To avoid this a suboptimal flight plan can be filed, asking for an inefficiently low altitude or a longer less congested route.

Once airborne the part of the pilot's job is to fly as efficiently as possible so he/she might then try to convince air traffic control to allow him to fly closer to the optimum route. This might involve requesting a higher flight level than in the plan or asking for a more direct routing. If the controller does not immediately agree it may be possible to rerequest occasionally until they relent. Alternatively if there has been any bad weather reported in the area a pilot might request a climb or turn to avoid weather. As air traffic controllers do not know the precise location and height of pockets of turbulence, they would not know if the pilot was exaggerating the problem to get a more efficient route.

Even if the pilot does not manage to revert to the optimal route the benefits of being allowed to fly may well outweigh the cost of the suboptimal route.