Under what conditions does a real gas obey the relation $PV = RT$?

$A$ real gas behaves as an ideal gas at

Ten small planes are flying at a speed of $150 \ km/h$ in total darkness in an air space that is $20 \times 20 \times 1.5 \ km^3$ in volume. You are in one of the planes, flying at random within this space with no way of knowing where the other planes are. On the average, about how long a time will elapse between near collisions with your plane? Assume for this rough computation that a safety region around the plane can be approximated by a sphere of radius $10 \ m$.

The mean free path and the average speed of oxygen molecules at $300 \ K$ and $1 \ atm$ are $3 \times 10^{-7} \ m$ and $600 \ m/s$,respectively. Find the frequency of its collisions.

The mean free path of a molecule of diameter $5\times10^{-10} \ m$ at the temperature $41^{\circ}C$ and pressure $1.38\times10^{5} \ Pa$ is given as . . . . . . $m$. (Given $k_{B}=1.38\times10^{-23} \ J/K$).

Under which of the following conditions is the law $PV = RT$ obeyed most closely by a real gas?