Dick;
We once had a Minister for Transport. His Title was Minister for Rural and Regional Affairs and Transport. Indeed the Senate Estimates refer to transport matters in that acronym. Truss hasn't that 'handle' any more. Indeed I don't think he knows anything about aviation except for what he is told by his 'Handler' (minder) Senior Public Servant Mike MrDak.
I was once a constituent of his in the old Wide Bay/ Burnett Electorate and he was spectacular in his ability to constantly achieve nothing on a range of matters including aviation.
I'm reliably told by different people that he is not contesting the next election and Barnaby Joyce is the Heir apparent. By this advice I imagine he is 'marking time'/'treading water' /and generally 'biding his time' until his retirement and all the perks arrive. I doubt he wants to waste energy on any project that may upset these arrangements. Aviation being the 'hot potato" it is he will waste no metaphors in 'ducking for cover' at the mere mention of it.
I currently live in a Nationals Electorate but I'll not be voting for them at the next election. My Member refers all my aviation emails to Truss who has a standard letter sent back to the sender who on-forwards this to me also by 'snail mail'. My Member is living off the good will of the last incumbent who was a most worthwhile Member. Many here believe he is a goat and won't also be voting for him.
If Truss decides not to contest the next election, I would wager his electorate may have similar qualms to mine and those I talk with. His Electorate may become 'marginal'.
In answer to your first question/ paragraph... I can't think of one time.