Final answer:
The question is about non-RVSM airspace cruising altitudes under IFR between FL290 and FL600, requiring a vertical separation of 2000 feet between aircraft for safety in these flight levels.
Step-by-step explanation:
The question refers to Instrument Flight Rules (IFR) cruising altitudes, specifically in the non Reduced Vertical Separation Minimum (RVSM) airspace between flight levels 290 (29,000 feet) and 600 (60,000 feet). In non-RVSM airspace, aircraft are required to maintain a vertical separation of 2000 feet to ensure adequate safety margins. This means that suitable altitude levels for East/West-bound flights are typically organized in a specific pattern to prevent collisions and ensure traffic flows smoothly.
For example, for East-bound flights in the Northern Hemisphere, aircraft might fly at odd-numbered flight levels like FL290, FL310, FL330, etc., while West-bound flights might fly at even-numbered flight levels like FL300, FL320, FL340, etc. However, as the RVSM was implemented to reduce the vertical separation above FL290 from 2000 feet to 1000 feet, it allows more aircraft to safely share the airspace and increases the capacity of air traffic paths. In cases where RVSM is not applicable, due to perhaps aircraft equipment restrictions or regional air traffic regulations, the original 2000 feet separation must be maintained.