More than 10,700 flights in the United States were delayed on Friday, July 17, 2026, as smoke from over 900 active wildfires in Canada caused hazardous air conditions. The disruptions affected airports across the US Midwest, Great Lakes, and East Coast regions. Hazardous air quality persisted for six consecutive days, impacting more than 100 million Americans across 18 states.
Airline Waivers and Airport Disruptions
United Airlines issued a travel advisory on July 17 covering 17 airports in the US and Canada, including Detroit, Toronto Pearson, Buffalo, Syracuse, Rochester, Duluth, and airports across Michigan, Wisconsin, and New York. Passengers could rebook flights scheduled for July 17
or 18 without change fees until Monday, July 20, 2026.
Delta Air Lines released a Midwest Air Quality Advisory covering Detroit, Minneapolis-St. Paul, Milwaukee, Green Bay, Grand Rapids, Madison, and additional cities in Michigan and Wisconsin. Their no-fee rebooking window for affected flights runs through Tuesday, July 21, 2026.
American Airlines experienced delays on 42 percent of its flights on July 17, more than double its 2026 average of approximately 20 percent. The airline’s waiver for no-cost rebooking ended on July 18, 2026. Passengers who missed the deadline may apply the unused ticket value toward future travel within one year
of ticket issuance.
Philadelphia International Airport recorded 365 flight delays and 12 cancellations on Thursday, July 16, 2026. The FAA implemented a ground delay program there, contributing to more than 200 delays on Friday. Smoke-induced reduced visibility affected flight operations, complicating FAA controller efforts beyond typical weather rerouting challenges.
Hazardous Air Quality Across US Cities
Air quality measurements reached hazardous levels in multiple cities. Detroit recorded an AQI near 600 on July 16, surpassing its previous all-time record. Northern Minnesota registered PM2.5 concentrations above 600 micrograms per cubic meter on July 16 and 17, far exceeding the Environmental Protection Agency’s hazardous threshold of 500.
Chicago’s air
quality index was approximately 153 at 6 a.m. on Sunday, July 19, making it the second worst globally among major cities according to IQAir data. Philadelphia, Milwaukee, Pittsburgh, and Washington, D.C. also ranked among the worst polluted at various times during the week.
The National Weather Service warned a third wave of Canadian wildfire smoke would move into the Great Lakes region on July 19, with unhealthy air continuing in Chicago, Detroit, and parts of the Northeast.
The EPA advised all individuals to limit outdoor activities when the AQI surpasses 150, with recommendations to avoid outdoor exertion entirely if it
rises above 200. N95 or KN95 masks filtering particulates are recommended, while standard cloth masks offer limited protection.
Trade and Political Responses Amid Smoke Crisis
On July 17, President Donald Trump threatened to add the costs of wildfire smoke pollution to existing tariffs on Canada. He cited “willful negligence” in Canadian fire management and announced plans to discuss the issue with Canadian Prime Minister Mark Carney. Trump stated these costs “must of necessity be added to the TARIFFS Canada is currently paying.”
Legal experts note that following a Supreme Court ruling in February 2026, the president’s authority to impose tariffs under the International Emergency Economic Powers Act
was restricted. The 10 percent global tariff under Section 122 of the Trade Act is set to expire on July 24, 2026, while Section 301 requires a finding of unfair trade practices, which wildfires do not constitute. US Trade Representative Jamieson Greer formally declined to renew the Canada-United States-Mexico Agreement as of July 1, 2026.
Canadian Prime Minister Mark Carney responded that tackling climate change is “the responsibility of all countries, including the United States.” Emergency Management Minister Eleanor Olszewski said Canada has invested $12 billion since 2020 on forest sustainability and fire prevention. Ontario Premier Doug Ford called Trump’s
tariff threat a “shame” and urged lifting US softwood lumber tariffs, currently above 45 percent including a 10 percent increase imposed in October 2025.
Climate Change Drives Wildfire Severity
The cluster of fires in Ontario and Minnesota ignited on July 13, 2026, amid a record-breaking heat wave. Chief Meteorologist Shel Winkley of Climate Central stated that “these temperatures would be virtually impossible to occur on July 13 in Ontario without the influence of climate change.” Climate scientist Daniel Swain attributed the intense heat and dryness to rapid fire growth fueled by thunderstorms and lightning strikes.
The National Interagency Fire Center reported US wildfires have burned
more than 5,740 square miles in 2026, 31 percent above the 10-year average. Canada’s wildfire season is tracking at 134 percent of its 10-year average through mid-July, although it has not reached the 2023 record total.
The Trump administration has reduced wildfire smoke research capacity by closing labs, including the Pacific Wildland Fire Sciences Lab in Seattle, which provides critical wildfire and smoke forecasting data relied upon by firefighting agencies.
