WestJet planes flew with the lowest percentage of empty seats in the airline's history last month, the Calgary-based airline said today.

The plane had a load factor of 88.9 in August, the highest point in the airline's 16-year history.

"We are extremely pleased to report the highest single-month load factor in WestJet history," CEO Gregg Saretsky said. "The demand environment remains strong and we are seeing a growing contribution from our airline code-shares and interline partnerships."

Revenue passenger miles, a closely watched industry metric that tracks traffic, increased 9.2 per cent year over year. That was more than enough to outpace growth in capacity, which grew 2.3 per cent over the same period. The company flew 172,000 more guests in August over last year.

Record month at Porter

Toronto-based Porter Airlines, which serves short-haul flights from the Toronto Island Airport downtown, reported an August load factor of 74.5 per cent, up from 68.7 per cent a year ago.

Passenger numbers increased 23.8 per cent from the previous year, and the airline carried a record 260,000 passengers during the month.

"This is the best month we've had in nearly six years of operating," Porter founder and CEO Robert Deluce said.

Air Canada also reported a record load factor for August. The airline said its load factor for the month was 87.9 per cent, versus 87.8 per cent in August 2011.

"Led by increases in traffic in the Australia, Caribbean, Mexico and Central and South America markets of 7.9 per cent overall, and the domestic Canada market of 3 per cent, we generated system wide traffic growth of 0.7 per cent on a capacity increase of 0.6 per cent," said Air Canada president and CEO Calin Rovinescu.