There are plans to extend the runway in Foula by at least 86 metres to guarantee the future of air services following a change in regulations.
A warning has been made that without the extension the lifeline service would have to end.
New rules around braking distances mean that the existing length of runway is only suitable for landing in dry conditions, and is not technically long enough for wet conditions.
Approval is currently in place from the Civil Aviation Authority (CAA) to allow Shetland Islands Council’s islander plane to land at Foula in wet conditions on the existing runway.
But there is a warning that the safety case behind this approval may not be able to be granted in the future due to possible changes in the legislation underpinning it.
The council is proposing to extend the runway to ensure that landings are not restricted to dry conditions only in the future.
There are also plans to license the airstrip. An exemption is currently in place to allow scheduled flights to land at Foula without an aerodrome licence being in place.
The current licence exemption runs until March 31, 2023.
A full planning application has now been submitted for the airstrip extension.
An environmental impact assessment submitted with the plans said it is important that the work can go ahead as soon as possible due to the weather.
Airtask currently runs flights between Tingwall Airport and Foula, as well as to Fair Isle.