'Regular talks' on Scotland-US nuclear material flights
The Scottish government said it has "on-going regular dialogue" with the UK government on the transfer of nuclear material from Scotland to the US.
Highly-enriched uranium was transferred from Dounreay, near Thurso, to the US via Wick John O'Groats Airport in 2016.
The transfers were made following a deal agreed by UK and US governments.
The airport, 30 miles from Dounreay, is run by Highlands and Islands Airports Ltd (Hial), a public corporation owned by Scottish ministers.
Further flights of the material, in exchange for a type of uranium from the US used to diagnose cancer, are expected in the future.
Highlands Scottish Greens MSP John Finnie has raised concerns about the suitability of Wick John O'Groats Airport in a series of questions to the Scottish government.
The MSP does not believe the airport to be safe for the large aircraft involved.
In answer to one of his questions, Environment Secretary Roseanna Cunningham said: "There will be on-going regular dialogue between the Scottish government and the UK government on the programme of movements of nuclear materials from Dounreay.
"The Scottish government will continue to seek assurances on the safety and security of any movements."
Mr Finnie has also asked what role Hial played in negotiations about the flights and also what extra costs Police Scotland has incurred in helping to provide security for the flights.
The government is expected to release responses to his other questions later on Tuesday.
Dounreay, near Thurso, is being decommissioned and the site cleaned up.
Most of the radioactive materials held there, such as fuel, are being moved to other locations, including Sellafield in Cumbria where it will be reprocessed or stored.
These shipments are being made by rail.
Other material has been returned to nuclear sites overseas.
During the 1990s, nuclear material was sent from abroad to Dounreay for reprocessing.
The customers included power plants and research centres in Australia, Germany and Belgium.
Dounreay said the priority "at all times" was to comply with regulations governing "the safe and secure transportation of nuclear material, both in storage and transit".
The Nuclear Decommissioning Authority provided Hial with funding to upgrade the airport in preparation for the US flights.