Global airline passenger traffic growth slowed to an eight-month low of 5.5% year-over-year (YOY) in September, down from 6.4% the previous month, according to IATA’s Air Passenger Market Analysis.

While the September rate was in line with the 10-year average, it fell short of the 6.7% year-to-date growth rate.

The slowdown was “likely owing to the anticipated reduced demand boost from lower airfares due to rising airline cost pressures,” IATA DG and CEO Alexandre de Juniac said, adding that “heightened uncertainty about trade policies and mounting protectionist policies may also be having an impact.”

The slowdown in traffic growth also reflects disruptions caused by hurricane and typhoon activity, particularly in Japan. However, even when accounting for that impact, the seasonally adjusted rate of growth slowed over the third quarter, which IATA economists called “the clearest indication yet of the extent to which we are seeing a reduced boost to demand from lower airfares than we have seen in recent years.”

The industrywide passenger load factor fell for the first time in eight months, edging down 0.3 points YOY to 81.4% on 5.8% capacity growth. While North American carriers saw load factors drop 1.3 points to 80.7%, airlines in Asia-Pacific, Europe and Africa managed to post records for the month.

Elsewhere in the report, de Juniac issued a warning that governments need to begin investing more heavily in infrastructure to support the doubling in demand IATA expects over the next 20 years. He pointed to the decision to cancel construction on a new international airport in Mexico City as a “backward step that will have will have negative economic ramifications” for Mexico and the entire Latin American region.

Ben Goldstein, Ben.Goldstein@aviationweek.com