My vote is strongly for complicit and not "head in the sand"
In CASA's case, I would vote for conspiracy.
Either the Board has failed to act on executive advice (unlikely) or the Board has not received the full story from the executive (more likely), despite this statement:
"Hello Mr Buckley Following your previous correspondence, the Chair of the CASA Board, Tony Mathews, asked me to assure you the Board has been kept abreast of what has been done by CASA so far to address your concerns and has advised management they need to be kept informed going forward.Best regards"
One or both of these entities is telling porkies.
Hopefully, it will all come out in an open forum.