Travel disruption caused by snow and poor visibility has been blamed for a slight dip in passenger numbers at Glasgow Airport last month.
Almost 412,000 people travelled through the airport in January, 1.2% less than the same period last year.
However, managing director Amanda McMillan said the underlying performance remained strong, with the introduction of two new routes next month.
"Given the positive start we made to the year with the news 2012 had been our busiest year since 2009, it was frustrating to see passenger numbers take a slight dip as a result of poor weather conditions elsewhere," she said.
"However, in terms of route development we continued to make significant progress, carrying on where we left off in 2012, with the announcement Wizz Air will operate flights to Warsaw and Gdansk from March.
"The addition of two major European cities to our list of destinations is particularly pleasing as was the decision by Flybe to introduce a year round service to Shannon in the west coast of Ireland."
Meanwhile, Aberdeen Airport recorded its 24th month of consecutive growth in January, with a 0.6% increase in passenger numbers compared to the same period last year.
There was growth in both the domestic and international markets, it said, but a decline in helicopter numbers affected the traffic figures, which were down 11.1%.
Derek Provan, Aberdeen Airport managing director, said: "The ongoing issues with the helicopter fleet are having an impact on our figures, and we are working closely with all three operators to understand their respective operational issues.
"We had a positive year in 2012, and we are starting 2013 with further growth, however this set of figures reflects how challenging the market remains."