Myth: Pilots turn off air conditioning packs to save fuel.

Fact: While the flight deck does have the capability to shut down an air conditioning pack in the event of a malfunction or abnormality, this is not intended for fuel-saving purposes. In fact, on many Boeing airplanes, when one pack is shut down the remaining air conditioning system automatically goes into a high-flow mode to compensate for much of the capacity of the unit that is turned off. Of course, that means that more air is being taken from the engine compressors by the portion of the system still operating, so there is little to be gained from a fuel-efficiency standpoint. Some early 747s (not 747-400s) do have an economy setting that can be used to save fuel through reduced air flow. This is intended for use at operator discretion when passenger loads are light. However, that feature is no longer offered and, in any case, Boeing recommends all packs be operated at the normal standard setting whenever passengers are on board.