The funicular railway at Cairngorm Mountain will remain closed during winter while repair works run months behind schedule.
It had been hoped strengthening works on the one-mile viaduct would be completed early next year.
However, Highlands and Islands Enterprise say Covid and spring blizzards mean the project will now extend into the second half of 2022.
The mountain resort will, however, stay open through winter with skiers and snowboarders able to access the slopes using nine tows.
Repairs one of ‘most complex and difficult’ in Scotland
The funicular railway opened in 2001 but was taken out of service in 2018 after an inspection revealed structural defects.
No trains have run on the tracks since then with HIE taking the builders and designers to court in a £14.5million legal action against the owners of Morrison Construction.
Repairs have been approved by the Scottish Government as part of a £20.5million package for the wider estate, which will aim to make it an all-year destination.
Warnings have been made the delay could also push costs upwards with a revised budget for the funicular repairs to be published “as soon as it is possible to do so”.
Carroll Buxton, interim chief executive of HIE, said Covid and extreme blizzards in spring had pushed the timetable back – but also warned construction materials were in short supply across the UK.
She said: “We’ve always been upfront in describing the reinstatement programme as one of the most complex and difficult civil engineering projects in Scotland.
“As well as managing technical challenges, the team has to take great care to protect the mountain environment, and deal with difficult terrain and extreme weather conditions that can quickly become hazardous.
“The original schedule was very ambitious, even without the impacts of the pandemic lasting as long as they have and before the more recent problems in sourcing construction materials of suitable quality.”
Highlands and Islands MSP Edward Mountain described the postponement as “deeply disappointing” while calling for “honest and transparent” updates about the project.
He said: “That reopening date always appeared to be very ambitious and I’m not surprised the project has now encountered delays given the complexities of the repair work.
“We now need to know why HIE raised expectations that it could be completed by early next year and when it became clear that the repairs would delay reopening the funicular for around six to nine months.”
What other improvements are being made?
HIE wants to broaden the appeal of Cairngorm Mountain to make the resort a year-round destination for visitors.
A 25-year masterplan vision has been published with hopes to bring mountain biking to the slopes as well as exploring alternative transport options, electrifying snow cannons and a possible new chair lift at Coire Cas.
A £780,000 refurbishment for the Ptarmigan building, which houses the UK’s highest restaurant as well as a shop and exhibition has already been approved.
It is hoped work on the renovation will start by the end of August and be completed by the end of this year.