Different types of low-carbon emission aircraft are to be tested on routes between islands in Orkney.
The 18-month project forms part of long-term plans to reduce harmful emissions in the Highlands and Islands.
The trial will include electric and hydrogen-powered planes, as well as drone deliveries.
The aim is to eventually create the "world's first zero emission aviation region" in the Highlands and Islands.
The Scottish government said this would be achieved by replacing fossil fuels with electric, hydrogen and other low-carbon fuels at Highlands and Islands Airports Limited (Hial)-run airports and also on the aircraft serving them.
Plans for the trials were first announced by the Scottish government as part of its programme for 2019-2020, and Hial has received £3.7m in funding.
What has been described as the "UK's first operationally-based, low-carbon aviation test centre" is to be set up at Orkney's Kirkwall Airport.
The site will lead the work trialling different aircraft on short inter-island routes.
Drones for potential use in delivering medical supplies will also be flown as part of the trial.
UK Research and Innovation is also part funding the Sustainable Aviation Test Environment, a project involving Hial and business in Orkney and in Caithness in the Highlands.
Scotland's Transport Secretary Michael Matheson said the project was an "important step" towards "decarbonise scheduled passenger flights" within Scotland by 2040.
He said: "This is a very exciting project and it's fantastic to see Highland and Islands Airports Ltd take the lead to create the UK's first low-carbon aviation test environment."
Hial's managing director Inglis Lyon said the project would put the Highlands and Islands "at the vanguard of the adoption of next-generation aircraft".