More than 900 wildfires burning across Canada produced hazardous air for six days, causing delays to over 10,700 US flights on July 17, 2026. Smoke exposure affected over 100 million Americans across 18 states, mainly in the US Midwest, Great Lakes, and East Coast regions.
Major Airlines Issue Travel Advisories and Waivers for Affected Flights
United Airlines issued an air quality travel advisory on July 17 covering 17 airports including Detroit, Toronto Pearson, Buffalo, Syracuse, Rochester, Duluth, plus Michigan, Wisconsin, and New York airports. Passengers with tickets bought by July 16 could rebook flights scheduled for July 17-18 without a change fee or fare difference within the same cabin class
and city pair, with rebooking closing July 20.
Delta Air Lines issued a Midwest Air Quality Advisory from July 16 to 18 for airports including Detroit, Minneapolis-St. Paul, Milwaukee, Green Bay, Grand Rapids, and Madison. Delta passengers could rebook flights without fare differences through July 21. American Airlines experienced a 42% delay rate on July 17, more than double its 2026 average of 20%. Its broad waiver policy for 29 airports expired on July 18, though passengers may apply unused ticket value toward future travel within one year.
FAA Ground Delay Program and Air Traffic Control Slowdowns
The Federal Aviation Administration (FAA) implemented ground delay programs at Philadelphia International
Airport, resulting in 365 delays and 12 cancellations on July 16, and over 200 delays on July 17. Wildfire smoke reduced visibility, forcing air traffic control to slow operations, contributing to widespread delays. Travelers faced longer connection times at major hubs including Philadelphia, Chicago O’Hare, Detroit, and Great Lakes airports.
Air Quality Reaches Hazardous Levels in US Cities
A third wave of Canadian wildfire smoke affected the Great Lakes region by July 19, with Chicago’s Air Quality Index (AQI) reaching 153, ranking as the second worst among major global cities that morning. Northern Minnesota and Detroit recorded severe PM2.5 concentrations around 600 micrograms per cubic meter, exceeding the
Environmental Protection Agency’s hazardous level threshold of 500. Cities including Chicago, Milwaukee, Pittsburgh, and Washington also consistently topped global poor air quality charts during the week.
The EPA advised limiting outdoor exertion at AQI levels above 150 and avoiding outdoor physical activity above 200. N95 or KN95 masks were recommended for protection against fine particulate matter, which standard cloth masks do not adequately filter.
Trade Tensions and Climate Context Behind the Wildfires
On July 17, 2026, President Trump posted a threat to add the “incalculable” cost of Canadian wildfire smoke pollution to existing tariffs on Canada. However, legal experts note the Supreme Court ruled on February 20, 2026,
that the president lacks authority under the International Emergency Economic Powers Act to impose tariffs. The Trump administration currently relies on a 10% global tariff under Section 122, set to expire on July 24, 2026.
Canada’s Prime Minister Mark Carney highlighted climate change as a collective responsibility and criticized US climate policy rollbacks. Emergency Management Minister Eleanor Olszewski stated Canada has invested $12 billion in forest sustainability and fire prevention since 2020. Ontario Premier Doug Ford challenged the US to lift softwood lumber tariffs exceeding 45%, including a 10% duty imposed in October 2025, linking tariff relief to continued Canadian
forest management support.
Scientists attribute the wildfires to an unprecedented North American heat wave, with Michigan temperatures on July 13 recorded as 25.2°F above average. Shel Winkley, chief meteorologist at Climate Central, said the July 13 heat would be virtually impossible without climate change influence. The National Interagency Fire Center reported US wildfires in 2026 have burned 31% more land than the 10-year average, while Canadian wildfire activity reached 134% of its 10-year average through mid-July 2026.
Meanwhile, the Trump administration has targeted wildfire smoke research facilities for closure, including the Pacific Wildland Fire Sciences Lab in Seattle, which supplies
critical fire and smoke mapping for governmental and firefighting agencies.
