By Kevin Keane
BBC Scotland's environment correspondent
Scotland's first electric-powered aircraft has taken to the skies from a new test centre in Orkney.
One of the twin engines in Ampaire's six-seater Cessna Skymaster has been replaced with an electric motor.
The company believes it could pave the way to retrofitting inter-island and short-haul flights with greener technologies.
It is the first low-carbon aircraft to fly at the £3.7m sustainable aviation facility based at Kirkwall airport.
The plane was built in 1974 but has been retrofitted at the company's headquarters in California.
After initial test flights in Hawaii, it was shipped to Scotland for its first flight across open water between Orkney and Wick, a 37-mile (60km) flight.
Test pilot Justin Gillen told BBC Scotland: "It's the only hybrid-electric airplane that I know of flying today.
"As the airplane is approaching, you hear the propeller which is a kind of blade-through-air sound and then you hear the throatier sound of the engine. With our electric engine, you hear the propeller but that's pretty much it."
On Ampaire's aircraft, the engines are built at the front and back of the cockpit in a "push-pull" design.
It's the front engine which has been replaced with an electric motor that's a fraction of the size.
A huge battery pack has been attached to the underbelly which can keep the aircraft running for several hours in the right conditions.
About 90 minutes of rapid charging would provide around an hour of flight.
Susan Ying from Ampaire said: "It will fly cleaner, be more efficient and more economical.
"It will start as a short-haul but eventually, as the technology's improving, it could go into medium to long-haul."
That would require batteries to continue shrinking but the developers are confident that will happen.
Air travel is a notoriously difficult industry to decarbonise because the aviation fuel has a high energy density.
But it's a high emitter of carbon dioxide which needs to be reduced to net-zero if we are to halt climate change.
Island air links in Scotland are regarded as "lifeline" for communities who live there, and so battery-powered flights are under serious consideration.
Dougie Cook, from Highlands and Islands Airports, explained: "If aviation is to survive throughout the world, then it needs to decarbonise and it needs to do so quite quickly. So this is a really important first step.
"The links around Orkney are called lifeline links for a reason and it's absolutely essential that we keep them going so electric aviation will guarantee that and make it sustainable for the future."
Flights currently operate from Kirkwall to six of the furthest islands – Eday, Sanday, Stronsay, North Ronaldsay, Westray and Papa Westray.
The test facility is expecting to play host to other forms of low-carbon flights, including hydrogen and sustainable aviation fuels.
Emergency services rush to attend car and motorbike crash on Aberdeen roundabout
‘We really need you’: Blood bank expands capacity in Aberdeen and Inverness as stocks run low
Friday courts round-up – Man drove at 100mph on AWPR and the drink driver who missed his bus
Toddler slips out of Northfield nursery and gets home to mum – who is told by staff ‘he’s in the garden’
Keith woman's Doric stories are homage to Portessie
Red Ensign flag raised by Moray Council
Information about BBC links to other news sites
Fate of Afghan holdout valley hangs in balance
Reports of heavy fighting continue in Panjshir Valley, as both sides claim to have the upper hand.
Life under the Taliban: Where is your male escort?
Capitol riot: 'QAnon Shaman' pleads guilty
Paddle boarder's 'magical moment' with whales. Video
Africa's top shots: Power, prayer and pig masks
Meet Shang-Chi – the MCU's first Asian superhero
The dream that started at the supermarket
Child sex abuse lawsuits find prince and priests
Quiz of the week: What did Ronaldo get up to?
'I had breakfast with North Korea's first leader' Video
Archive: Afghanistan's forgotten era on film
How Europe's relationship with Joe Biden turned sour
Have you been getting these songs wrong?
What happens to your body in extreme heat?
Fate of Afghan holdout valley hangs in balance1
Capitol riot: 'QAnon Shaman' pleads guilty2
In Kabul, Afghans adjust to a new, uncertain fate3
Woman convicted of Cyprus gang-rape lie appeals4
Child sex abuse lawsuits find prince and priests5
Teenage boxer dies days after knockout6
How Europe's relationship with Joe Biden turned sour7
Cranberries singer O'Riordan died by drowning8
Brazen coyotes terrorise British Columbia park9
Ex-prosecutor faces charges over black jogger case10
© 2021 BBC. The BBC is not responsible for the content of external sites. Read about our approach to external linking.
By Kevin Keane