Aberdeen International Airport (AIA) has suffered a decline in its monthly passenger figures for the first time since April 2017.
A total of 276,391 people used the north-east terminal in June, which was down by 4% on the same month in 2017.
Highlands and Islands Airports (Hial) is due to announce figures for the first six months of the year within days.
But the Civil Aviation Authority (CAA) has revealed June 2018 numbers for some of Hial’s 11 airports.
Benbecula was up by 16% at 3,312, while Campbeltown suffered a 15% drop to 835, Islay was down by 6% at 3,358 and Wick John o’ Groats fell 4% to 1,606.
Hial’s figures are expected to show a flat performance at Inverness Airport over the six months but a big increase at Sumburgh in Shetland.
Among other Scottish airports included in the latest CAA data, Tingwall in Shetland was used by 470 people in June – down from 488 a year earlier.
AIA’s drop came after 13 consecutive months of growth in an improving north-east economy.
Bosses said the June reversal was driven by a fall in the number of passengers using international services.
A spokeswoman for the airport added: “Whilst domestic traffic was up, we saw a decline in international traffic which was in part due to the withdrawal earlier this year by Lufthansa of its Frankfurt route and Icelandair’s decision to end its Reykjavik service.
“We continue to operate in what is a challenging market.”
AIA’s spokeswoman also highlighted air passenger duty as a “very real barrier to growth” at the gateway.