At the beginning of this series of articles Mr. Major sought a definition of the word “airworthiness”. Having consulted the Concise Oxford Dictionary he was clearly less than satisfied with the simplicity of the dictionary's definition that “airworthy” meant “fit to fly”. Certainly this seems to be a very simple phrase to encompass such a complex subject which in turn depends upon so many engineering and personal disciplines. However, it is a simple and concise statement; it is also the corner stone of the advice handed by the Air Navigation Order to the Civil Aviation Authority in respect of its duty in relation to issuing a United Kingdom Certificate of Airworthiness — that is the Authority must be satisfied that the aircraft is fit to fly having regard to the things such as design, construction, flight trials and so on that we readily associate as having a direct bearing on the safety of an aircraft.