David Henderson was born in Glasgow on August 11th 1862, the youngest son of David Henderson and Jane Pitcairn. Between 1877 and 1880 he studied engineering under Lord Kelvin, most likely with the intention of joining the family business of shipbuilding.
However, during his fourth year he left Glasgow, and continued his education at the Royal Military Academy Sandhurst. In 1895 he married Henrietta Dundas with whom he had a son and a daughter. His son Ian eventually became a captain and a pilot for No.19 Squadron in the RAF, but died in a flying accident in 1918.
After David's graduation from Sandhurst in 1883 he joined the 1st batallion Argyll and Sutherland Highlanders, and shortly thereafter served in South Africa, Ceylon and China. During the second Boer war, David Henderson became an intelligence officer. Between 1900 and 1902, he served as the director of military intelligence under Lord Kitchener.
It was during this role that he brought a new scientific approach to gathering and collecting information to the military. He eventually wrote two books on the subject, Field Intelligence: Its Principles and Practice (1904) and The Art of Reconnaissance (1907). He highlighted the usefulness of aerial reconnaissance in these, and was eventually inspired to get his own aviation license.
In 1911 he became the oldest pilot in the world, aged 49. He became known as the Father of the Air Force, and he was awarded the honours of Knight Commander of the Order of the Bath, and Knight Commander of the Royal Victorian Order in 1914. He was the first person to go on Glasgow University's Roll of Honour, and he received an Honorary Doctor of Law.
Sources and further information: https://www.rafmuseum.org.uk/blog/the-forgotten-father-of-the-royal-air-forc/