Qantas will more than double the number of flights between Adelaide and Kangaroo Island after a decision by Regional Express to withdraw from the route.
The airline will now run 12 return flights each week, an increase on the existing five.
"Now is the time to be supporting Kangaroo Island, not deserting it," QantasLink chief executive John Gissing said on Friday.
"What Kangaroo Island needs over the months and years ahead is for tourists to come back and a reliable air service is vital for that to occur."
Regional Express, or Rex, blamed "capacity dumping" by Qantas for making its Adelaide to Kangaroo Island services unviable.
The row between the two carriers came after the island was recently devastated by major bushfires which burnt through more than 210,000 hectares.
On Monday, Rex announced plans to withdraw its island services and to also quit the Sydney to Ballina route because of a downturn in demand and the poor outlook for the coming year.
It also complained to the Australian Competition and Consumer Commission accusing Qantas of going beyond competing on merits.
"Rex has to face up to the reality that it is not able to match Qantas' financial firepower and unlike Qantas, Rex is not able to continue servicing a money-losing route indefinitely," the company said in a statement.
But Qantas said it was simply giving regional consumers more choice.
Mr Gissing said everyone at the airline was proud to be helping Kangaroo Island get back on its feet.
"We continue to work closely with tourism agencies to get the message out to potential visitors from around Australia and the world that Kangaroo Island remains one of Australia's most idyllic destinations," he said.
Premier Steven Marshall said the extra flights by Qantas would give island tourism a major boost while federal Tourism Minister Simon Birmingham said the announcement offered tourists and locals certainty.
"The Kangaroo Island community can now be confident that regular flights to and from the Island will continue, ensuring visitors continue to access the incredible hospitality and natural beauty that Kangaroo Island has to offer," he said.
Qantas plans to revise current timetables to ensure its new flight schedules allow easy connections through Adelaide for both domestic and international tourists.
It also plans to continue its summer services between Melbourne and Kangaroo Island.