Final answer:
As minimum en route IFR altitudes have been established for designated airways and air routes, such minimum altitudes shall be applied when flying in accordance with IFR along airways or air routes within designated mountainous regions, except that aircraft should be operated at an altitude which is at least 2000 feet higher than the minimum en route IFR altitude, when there are large variations in temperature and/ or pressure.
Step-by-step explanation:
When flying in accordance with Instrument Flight Rules (IFR) along airways or air routes within designated mountainous regions, minimum en route IFR altitudes are established to ensure safe navigation. These minimum altitudes must be followed unless certain conditions exist.
If there are large variations in temperature and/or pressure, aircraft should be operated at an altitude that is at least 2000 feet higher than the minimum en route IFR altitude. This higher altitude provides an additional safety margin, considering the potential impact of temperature and pressure changes on the performance of the aircraft.
By maintaining a higher altitude in such conditions, pilots can account for any potential changes in air density, which can affect aircraft performance, especially in mountainous regions. This practice helps ensure safer flight operations and reduces the risk of encountering terrain-related obstacles.