Alderney's States is calling for a small airport runway extension to the west to be put out to tender.
The Policy and Finance committee says, rather than guesswork, the actual cost of the project - known as Option C - needs to be known so that a decision can be made.
The island wants to be able to accommodate larger aircraft, to safeguard its air-links.
“We are clear that an extended, modernised and widened runway makes the most sense and would future-proof the Island's air infrastructure.
We have heard some seriously inflated cost figures put forward in some quarters and to deny Alderney this option based on irresponsible guesswork would be a gross injustice to Alderney and its community now and in the future.
Only after tendering the project will the States in both islands be able to determine whether, as clearly indicated in the Outline Business Case, Option C+ really does represent the best value for both islands in the mid- to long-term." - P&F Chairman Bill Abel.
Alderney's States says lengthening the 877m runway and widening it by 23m would allow larger ATR aircraft to land and provide an extra 20,000 passenger seats a year.
It would also be able to accommodate a dedicated medical evacuation service and larger private aircraft.
The committee's comments come as more maintenance work will be done on the runway, taxiways and apron during July.
The work will take place mainly at night so as not to disrupt flights.
Repair work was done in July 2021.
Last December, officials said they hoped for resolution to the long-running debate over the future of the runway in early 2022.
Drop-in presentations were held in the community in March involving Guernsey's States’ Trading Supervisory Board and Policy and Resources Committee.
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