It has entered into an agreement with Scilly Isles Skybus to short-term lease a Twin Otter from them if it is needed.
The 19-seat Twin Otter is a similar-sized aircraft to the Dornier but with some operational limitations that the Dornier does not have, so Aurigny may need to amend schedules or complement the service with a boat if it is used.
The Skybus crew will be tested for Covid and must satisfy requirements outlined by Public Health before they operate any services.
Mark Darby, Aurigny chief executive, said: ‘Over the last six months our relationship with Alderney has greatly improved and we have been proud to have been part of their staycation success.
‘We want to maintain that rapport and therefore have put measures in place that we hope we may not need.
‘We understand the importance of connectivity to Alderney, especially at this time, and want to avoid any widespread disruption resulting from a single-aircraft operation.’
Aurigny owns four Dorniers.
One of the older planes needs to have its wing replaced, which will cost around £500,000, with the other Dornier, which is out of service, providing the wing.
In November, the airline said it was waiting for financing from the States to do the work.
A lack of a decision on the public service obligation for the Alderney route was said to be a factor in the decision-making process.
Last week, Policy & Resources president Peter Ferbrache said it has written to Aurigny about the PSO and, if accepted, the issue would be resolved.