Aurigny trislanders loan plan goes to Guernsey States
High maintenance costs and rising unreliability means planes flying to Alderney "must be replaced by the end of the year", it is claimed.
Six trislanders, operated by the Guernsey States-owned airline Aurigny, currently fly from Alderney to Guernsey and Southampton.
Aurigny chief executive Mark Darby said: "The cost of keeping them in the air is now prohibitively expensive."
The purchase of three second-hand Dornier 228 is expected to cost £3m.
Treasury Minister Gavin St Pier has asked the government to guarantee a loan or lend the airline the money.
The airline already has several loans guaranteed by the States, including one which has allowed them to purchase a 122-seat Embraer 195 jet for use on the Gatwick route.
The move follows a two-week trial of the 19-seat Dornier in November.
Five of the 16-seat trislanders could be sold to airlines in South America or Africa, but G-Joey, the airline's pin-up and mascot, could go on display in the island.
There is a lot of affection for the plane, which inspired a series of books and a fan club, with more than 3,500 people on the Save Joey the Trislander Facebook group.
Mr Darby said: "The [trislander] fleet's average age is 37 years and, at £470 per flying hour, their maintenance costs are almost the same as our much larger 72-seat ATR-72 turboprops."
Deputy St Pier said the Dornier would improve the company's finances by £100,000 by cutting operating costs and increasing capacity.
The airline had accumulated losses of £12.5m by the end of 2012 and was expected to make further losses last year.
A review of the aircraft is expected once it is clear what improvements will be made to Alderney airfield under a £100,000 project.
A decision on releasing the money for the purchase or guaranteeing a loan is due to be made in May.