Okay kids, stop rocking the boat.
The reason given was that the Department (one assume Dept of Transport) is updating their websites, which includes the AAIB.
Have you thought your case through before blurting out an opinion?
The PDF is a good format, I'm not contesting that and could be supplied alongside the HTML version. However, HTML is still a more "open" format than PDF.
1.5meg PDF files take an awfully long time to load on a dial-up modem rather as opposed to HTML.
Linkability into each case doesn't happen
Search facility doesn't cover PDFs, so searching for past incidents and trends can't happen.
Some "mere" points on accessibility, a factor which all .gov.uk Government websites are committed to. Be that those with slow access, poor vision, deafness...