More than 10,700 flights in the United States were delayed on July 20, 2026 due to heavy smoke from over 900 active wildfires burning in Canada. The wildfire smoke has impaired visibility across US airspace, particularly affecting the Midwest, Great Lakes, and East Coast regions.
Flight Disruptions and Airline Responses
On July 17, United Airlines issued an air quality travel advisory covering 17 airports including Detroit, Toronto Pearson, Buffalo, Syracuse, Rochester, Duluth, and locations in Michigan, Wisconsin, and New York. Passengers with tickets purchased on or before July 16 could rebook flights scheduled through July 20 with no fee or fare difference, provided travel remains
within the same city pairs and cabin. This waiver expired on July 20.
Delta Air Lines released a Midwest Air Quality Advisory for flights from July 16 to 18 at airports such as Detroit, Minneapolis-St. Paul, Milwaukee, Green Bay, Grand Rapids and Madison. Delta allowed free rebooking through July 21 for travel within the same cabin class. American Airlines reported that 42% of its flights were delayed on July 17, more than double their 2026 average. Their waiver for fee-free changes covering 29 airports expired on July 18, but customers may still apply unused ticket value toward future travel within
one year.
Philadelphia International Airport recorded 365 delays and 12 cancellations on July 16, followed by over 200 delays on July 17 due to a federally mandated ground delay program from the FAA. FAA controllers have found it difficult to reroute traffic around the smoke since it limits visibility in ways unlike typical convective weather disruptions.
Air Quality and Health Impact
The wildfire smoke has caused hazardous air quality for six consecutive days as of July 20, exposing more than 100 million Americans across 18 states to dangerous PM2.5 particle levels. On July 19, a third wave of smoke returned to the Great Lakes, with
Chicago’s Air Quality Index reaching approximately 153, placing it among the world’s worst-polluted major cities that morning.
Northern Minnesota recorded PM2.5 concentrations exceeding 600 micrograms per cubic meter on July 16-17, surpassing the EPA’s hazardous ceiling of 500. Detroit also reached an unprecedented AQI near 600 on July 16, breaking the city’s all-time record and exceeding New York City’s peak during the 2023 wildfire event. Cities including Chicago, Milwaukee, Pittsburgh, and Washington ranked among the global leaders in poor air quality on July 17.
EPA guidelines advise limiting outdoor activity at AQI levels above 150 due to health risks for
all populations and recommend complete avoidance of outdoor exertion above AQI 200. N95 or KN95 masks are effective against the fine particulate matter, while standard cloth masks do not provide adequate filtration. The FIFA World Cup Final at MetLife Stadium on July 20 in East Rutherford, New Jersey, is currently considered unaffected by the smoke conditions.
Political Responses and Legal Context
On July 17, former President Trump threatened via social media to impose additional tariffs on Canada to cover the “incalculable” costs of smoke pollution from the wildfires, calling Canadian fire management “Willful Negligence.” However, a February 20, 2026 U.S. Supreme Court ruling limits presidential
authority to impose tariffs under the International Emergency Economic Powers Act (IEEPA), complicating the legal basis for such measures.
Currently, tariffs are applied under Section 122 of the Trade Act but are set to expire on July 24, 2026. The White House is considering Section 301, which requires formal findings of unfair trade practices, a standard wildfire smoke events do not meet. Most Canadian goods under the Canada-United States-Mexico Agreement (CUSMA) are exempt from existing 10% Section 122 tariffs, which further complicates tariff threats.
Canada has spent $12 billion on forest sustainability and wildfire prevention since 2020, according to Emergency
Management Minister Eleanor Olszewski. Prime Minister Mark Carney stressed shared responsibility for climate change among all countries, including the US, and pointed to American withdrawal from climate initiatives under Trump’s second term.
Ontario Premier Doug Ford countered U.S. tariff threats, highlighting Canada’s firefighting assistance to California in 2025 and urging the removal of US tariffs on Canadian softwood lumber, which currently include a 10% duty added by Trump in October 2025, totaling more than 45% on some products.
Climate and Fire Science Background
Climate scientists attribute the 2026 Canadian wildfires to record-breaking heat across North America, not inadequate forestry management. On July 13, temperatures in
Ontario were 25.2°F above average, creating conditions for rapid wildfire ignition and spread. Climate scientist Daniel Swain noted that the heat wave dried out forests and lightning strikes sparked multiple fire outbreaks.
The National Interagency Fire Center reported that over 5,740 square miles of U.S. land had burned by mid-2026, 31% above the 10-year average. The Canadian wildfire season is at 134% of its 10-year average acreage through mid-July, though it has not surpassed the 2023 record season.
The Trump administration’s plan to close the Pacific Wildland Fire Sciences Lab in Seattle threatens the production of critical wildfire smoke maps
used nationwide. Researcher Ernesto Alvarado called the lab’s work on fire and smoke prediction essential for public safety and firefighting coordination.
