It amazes me that content like this is for free on line.

Indeed, but it should be noted that this book was first published in 2010 to coincide with the retirement of the RAAF’s F-111s. Therefore, Australian readers in particular, might be a little disappointed to find that the link takes them to a book they already have. Nevertheless, the book is excellent and the availability of a searchable PDF is a bonus to those who already prize their hard copy.