International search underway for solo sailor missing on yacht

An international search is underway for a solo sailor onboard a yacht which departed Hobart nearly a month ago.

The sailor was last heard from on December 5 and is now overdue for arrival in New Zealand.

The Australian Maritime Safety Authority (AMSA) is coordinating the search off Australia's south-eastern coast with assistance from Australian and New Zealand defence crews.

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This is the second day of the search, AMSA said in a statement.

"AMSA has tasked the Melbourne-based Challenger rescue aircraft and a Royal Australian Defence Force P-8A aircraft to search an area of 55,560 square kilometres for the overdue yacht," the statement said.

"Both Australian and New Zealand search and rescue authorities conducted search operations covering an area of more than 185,200 square kilometres.

"AMSA has tasked the Melbourne-based Challenger rescue aircraft and a Royal Australian Defence Force P-8A aircraft to search an area of 55,560 square kilometres for the overdue yacht."