August was a strong month for WestJet, with a record 2.1 million pax carried and a load factor of 86.5%, up 1.9% year over year.
Capacity was up 8.8%, but a traffic boost of 11.3% more than absorbed the extra seats.
The 2.1 million pax represented an increase of 105,000 more flyers than in August 2015.
"We are pleased with our 4th consecutive month of double-digit traffic growth as we welcomed on board the highest ever monthly number of guests in our 20 year history," said WestJet President & CEO Gregg Saretsky.
For the year to date, WS has filled 82.9% of its seats, up 1.7 percentage points. Traffic is up 10.0% on a capacity increase of 7.7%.