Air Canada, the county's No. 1 airline, said its planes flew less full last month even as smaller rival WestJet Airlines Ltd. said its flights were more crowded.
Air Canada, said its load factor, the percentage of available seats filled with paying customers, slipped 0.6 percentage points to 77.5 per cent from January, 2008, when the measure rose to a record for the month.
Traffic on Air Canada and its regional carrier Jazz, increased 4.1 per cent to 3.86 billion revenue passenger miles but that gain was more than offset by a 4.9 per cent rise in capacity, or available seat miles, to 4.99 billion.
"This result is close to last year's record load factor for the same month underscoring the ongoing effectiveness of our disciplined approach to capacity management in a difficult economic environment," Calin Rovinescu, Air Canada's chief executive officer, said in a statement.
WestJet, the country's No. 2 airline, said on Wednesday its planes flew fuller in January, helped by increased vacation travel.
The carrier said its load factor rose to a record high of 78.8 per cent from 76.8 per cent in January, 2009.
Traffic, or revenue passenger miles, increased 9.7 per cent year-over-year, while capacity, or available seat miles, rose by 6.9 per cent.
"As we continue to endure the challenges of an uncertain economy, we are happy to be starting 2010 on the right foot," said WestJet CEO Sean Durfy.
"These great traffic results help illustrate the success of our seasonal deployment strategy and the continuing strength of WestJet Vacations and the WestJet brand."
The company said it launched new services in January to several "sun destinations" in the United States and Mexico.
The airline has said that transition problems with its Sabre reservation system would hurt fourth-quarter results, which are expected Feb. 17. It has forecast a decline in revenue per seat mile of 11 per cent to 13 per cent from the year-before quarter.