Well developed states have aircraft following airways in an orderly fashion under full positive A.T.C. control with good v.h.f. communications. The least developed states on the other hand are overflown by aircraft each on its own desired track with little if any control or communications. Many emergent states have taken the simplest step on the road to civilization in the air; they have specified mandatory airways or routes. In the most primitive situation aircraft, usually few in number, are protected against the risk of collision by natural dispersion. In other words the sky is so big and aircraft are so small that, provided they are spread out, there is very little risk of collision. The broadcasting of position reports by aircraft by v.h.f. on 126·9 m enables pilots to resolve any potential encounters that may occur. This situation occurs over the western Sahara.