Passenger numbers at Aberdeen International Airport (AIA) slid by more than 5% during August, new figures show.
The terminal was used by a total of 321,442 people, down from 339,656 a year ago.
Weaker demand for UK flights drove the decline, with an 8.5% fall.
Helicopter passenger numbers were down by 6.6% amid the oil and gas downturn, but international flights saw a 0.9% increase.
AIA managing director Carol Benzie said: “We report a mixed set of figures this month with heli traffic and domestic travel showing a reduction on 2014’s record figures.
“International traffic has received a boost with our busy summer charter flights and with the popularity of Wizz Air’s new Gdansk route”.
AIA said it had enjoyed a busy start to September, with the airport welcoming thousands of visitors to the city for Offshore Europe 2015.
More than 25,000 passengers were expected to pass through the airport over the four days of the conference.