Firebrand Liberal Senator Bill Heffernan has called the Irish-born head of Qantas, Alan Joyce, "an old Irish bomb maker".

The comments were made as Mr Joyce appeared in front of a Senate estimates hearing in Canberra today.

Senator Heffernan initially asked if Mr Joyce came "from a long line of Irish bomb makers", before later calling him one.

"Mr Joyce if the power was yours, you know from being an old Irish bomb maker, if you had the choice, what would be the ideal pilot training?" he said.

The Qantas head laughed off the comment, and Senator Heffernan made several other wisecracks throughout the hearing.

He also joked about there being no whisky in the water and about having a beer during a three-minute break.

The Senator acknowledged that people have been offended by the bomb jokes, but then made the same comments to fellow Liberal Julian McGauran.

"Senator McGuaran are you, do you come from a long line of Irish bomb-makers, do you?" he said.

Senator McGuaran responded: "Irish, Bill, yes. Happy to be Irish ... but not bomb-makers."

The New South Wales senator is no stranger to controversy, with a long list of public faux pas to his name, including calling Julia Gillard "deliberately barren".