Only two planes will be available to fly on the Alderney routes from early 2020, Guernsey States-owned airline Aurigny has said.
One of its planes needs a replacement wing costing £500,000.
An Aurigny spokeswoman said the work could not be considered until the result of a public service obligation (PSO), launched in 2018, was known.
She said the airline needed "certainty" on the future of the Alderney routes before progressing with the work.
The PSO tender was originally launched in October 2018, but no bids were selected and it was re-launched earlier this year with a result expected early next year.
Aurigny currently serves the Alderney-Guernsey and Alderney-Southampton route with three of its four Dorniers after G-SAYE stopped flying in April.
The lifespan of the wings is determined by the number of take off and landings.
The spokeswoman said: "G-LGIS has around 300 landings remaining."
"Without certainty over the future of the PSO or further financial commitment we will only be able to provide a two-aircraft operation from early 2020," she added.
"Understandably, we do not wish to commit to this significant expenditure without further confirmation and funding from the States."
The re-winging is described as "extensive engineering and design work" that would take four to six months to complete.
The spokeswoman said it already had "a 'donor' wing and the expertise on hand".