The report, written by Frontier Economics, said the runway could net the island that much if there were an additional 61,000 visitors a year, or £201m. if there
were 20,000 visitors a year more.
It would take only another 8,200 visitors a year for the project to achieve break even over the period, a similar figure generated by the trialled, but now ended, London Southend route.
There were 858,230 air passenger movements in and out of the island last year.
The modelling looked at the effect on both businesses and visitor numbers, although it did not take into account the impact on individual airlines, including States-owned Aurigny.
Frontier Economics said its estimates were conservative and therefore concluded it was very likely the runway would add economic value over time.
In all three modelled futures, the report attributed the lion’s share of benefits to increased spend by visitors to the island, with a smaller fraction generated by benefits to local businesses in the finance sector.
The benefit for the finance industry was estimated at £21m. with 8,200 extra visitors, £86m. with 20,000 and a substantial £153m. if 61,000 were attracted to the island.
Other benefits include a probable reduction in fares and increased flexibility in travel options because it would allow larger airlines to use existing fleets to operate Guernsey routes.
This could, in turn, reduce costs for the 5,300 trips islanders made to the mainland for medical reasons through both fare reductions and more flexibility in timing, therefore likely reducing costs associated with hotels, meals and more.
However, the projections are based upon the continuation of Guernsey’s quasi-open skies policy, which has proven divisive.
The president of the States’ Trading Supervisory Board, Deputy Peter Ferbrache, said he was in favour of reviewing the policy in the States meeting earlier this week.
Furthermore, Economic Development president Charles Parkinson suggested that the forecasts could be revisited after the Covid-19 crisis due to the seismic shift in business prospects.
The report also suggested that noise levels could rise between 5% and 15% and also concluded that construction would require the in-filling of a valley east of the runway and the loss of two farmhouses and five houses.