Senate President Scott Ryan is considering whether to seek a permanent ban on hot air balloons and other aircraft flying directly over Parliament House.
Taxpayers have shelled out millions for security upgrades at Parliament House and the Senate president thinks it's only right the air above it should be secure too.
Scott Ryan recently discovered the long-held assumption that he and Speaker of the House Tony Smith were in charge of the airspace above parliament was in fact wrong.
This led to a kerfuffle over a hot air balloon the Greens wanted to fly over the building as part of a climate change protest last week.
The flight was banned by the Civil Aviation Safety Authority after the presiding officers applied for a 15-day restriction over the building.
Greens senator Larissa Waters quizzed Senator Ryan about that restriction on Monday, asking why the climate balloon was banned but when she arrived at work this morning there was another hot air balloon flying over the top of parliament.
"Why was there a different approach taken to this morning's balloon and last week's balloon bearing a climate emergency slogan?" she asked.
The answer boiled down to the Greens having made an application to parliamentary officers relating to the protest action - thus triggering the inquiry about airspace restrictions - while Monday's balloon flight hadn't done so.
But Senator Ryan didn't shy away from turning the air over parliament into a no-flight zone, saying he was considering asking CASA to make it permanent.
"We've put a lot of work into securing this building," he told the estimates committee hearing.
"I don't think it appropriate for the immediate airspace above the building to not have some restrictions upon it, given that we've put in so much work, both in terms of human resources with extra staff here and in securing the perimeter of this building, given the risk that it faces and its unique and iconic status.
"I didn't see the balloon this morning. I have not previously seen balloons directly above the building, I see them flying around."
Earlier, Senator Ryan revealed the final cost of upgrading security entrances had come to $1.88 million, up from an expected cost of $1.5 million, but the work finished a few months earlier than a revised timetable.
Work is still being done to install secure turnstiles for pedestrians approaching the entrances after he had asked for that to be delayed until the new doors were functional.