Aircraft have been profitably employed in a multitude of forest operations in many parts of the world. Their usefulness is, of course, greatest where the forest cover is extensive and more or less continuous and where ground access is difficult. In such situations, as, for example, in parts of the American continent and in some tropical areas, aircraft have become indispensable forest tools and are used for such varied duties as the survey and evaluation of the species composition and volume of the standing crop; the detection of outbreaks of fire, disease, and insect pests; the transport of men and materials for fire fighting; the application of chemicals, in either liquid or solid form, for the control of damaging insects, fungal disease, and rodents; the application of herbicides and fertilisers; the re-seeding of cut-over areas; and for surveys of wild life resources.