Turnbull government minister Sussan Ley claims she had no choice but to take expensive charter planes along two busy capital city routes, saying last-minute diary conflicts made commercial flights impossible.

Despite previously refusing to comment on the two flights - between Canberra and Melbourne in July 2014, and Canberra and Adelaide in May 2015 - Ms Ley's office now says she had legitimate reasons for the charters.

With her ministerial future expected to be decided as early as Friday afternoon, the commercial pilot has also now denied flying the charter planes herself despite posting pictures of herself in the cockpit.

Prime Minister Malcolm Turnbull is scheduled to hold a 2.45pm press conference in Sydney, expected to be about Ms Ley's future on the frontbench.