Figures released by Aberdeen Airport show the 3.5 million passenger total for last year was a decrease of 7% compared to 2014, which was a record high year.
However, 2015 was the airport’s second busiest year ever despite the fall.
Passenger totals for December saw numbers decrease by 14.1% to 243,259.
Carol Benzie, the airport’s managing director, said: “Clearly 2015 was not without its challenges as there is a direct correlation between our passenger traffic and the performance of the wider economy and the oil price.
“Despite the impact on helicopter and energy related traffic, our international passenger traffic, particularly in the latter part of 2015, has been showing an upward trend.
“This is a result of our efforts to further develop our route network, which was bolstered in June 2015 with the arrival of Wizz Air who launched the first direct flights between Aberdeen and Poland.”
She said the airline will also launch direct flights to Warsaw later this year and Icelandair will provide a new, year-round service to its hub in Reykjavik from March.
Elsewhere, Edinburgh Airport has experienced the busiest ever year at a Scottish airport after more than 11 million passengers travelled through it in 2015.
A total of 950,000 more passengers used the airport than in the previous year, taking the total to 11,130,584.
Glasgow Airport also reported record numbers, recording its largest ever annual rise in passengers after welcoming more than 8.7 million people last year – an increase of 13%.
Gordon Dewar, Edinburgh airport’s chief executive, said: “Last year we enhanced passenger choice by offering more routes and more destinations – and passengers responded by choosing to fly in and out of Edinburgh Airport in greater numbers than ever before.
“This unprecedented success of 11.13 million passengers through our doors highlights the draw of Edinburgh as a destination and the growing appeal that Scotland holds across the globe.”
He added: “Our international passenger figures for December show a 19% year-on-year growth; this is a strong indicator of our global ambitions and gives reason to be optimistic about further growth in the year ahead.”
Glasgow Airport, which celebrates its 50th anniversary this year, saw its busiest December on record by welcoming 569,000 passengers.
It also secured an extra one million passengers in 2015 compared to the previous year.
Amanda McMillan, managing director, said: “2015 was exceptional in so many respects and we start our golden anniversary year in an incredibly strong position.
“Welcoming an additional one million passengers through our doors last year was a huge accomplishment, but by far the most pleasing aspect was the extent to which we bolstered our connections to European cities such as Budapest, Prague, Milan and Bucharest.
“Over the coming months we will welcome two major flag carriers in the form of Air Canada Rouge and Air France, and a new service to Montreal will commence with Air Transat.
“With these airlines, and others, coming on board we anticipate that 2016 will be our busiest year ever – topping nine million passengers for the first time in our history and putting us on a trajectory towards 10 million.”
Transport minister Derek Mackay said Edinburgh Airport’s milestone was a “fantastic achievement”.
He added: “The airport’s success brings benefits to both the local and national economies.
“By improving our international connectivity, we give Scottish businesses improved access to global markets and make the country even more attractive as a destination for tourists.
“Edinburgh Airport already offers a wide range of destinations, but the Scottish Government’s plan to cut Air Passenger Duty will help encourage airlines to develop new routes as well as help sustain existing ones.”
