Over the past couple of weeks, social media has been flooded with photos and videos of the devastating wildfires burning across the American West, including pretty ominous views through plane windows. Then, on Monday, Alaska Airlines suspended all flight operations in Portland and Spokane for 24 hours due to the hazardous air conditions. We imagine we're not the only ones wondering: Is it safe for planes to fly through wildfire smoke?
"Commercial airliners fly through mild and moderate smoke without problems in most cases," aerospace engineer Ben Frank, the founder of aircraft maintenance software company Rotabull, told TripSavvy. "However, volcanic ash or very thick smoke can cause visibility and air quality issues, in addition to degrading jet engine performance."
It all boils down to the composition of smoke. "Smoke from wildfire contains different compounds such as carbon monoxide, volatile organic compounds, carbon dioxide, hydrocarbons, and nitrogen oxides, which are far from the hazard of volcanic ashes," explained José Godoy, CEO of flight operations company Simpfly. "Volcanic ashes are made up of tiny fragments of rock, minerals, and volcanic glass, which are hard and abrasive."
So while smoke typically gets pulled through a jet engine without a problem, the particles of volcanic ash can damage different surfaces of an aircraft. That’s why air traffic in Europe was halted during the 2010 eruption of Eyjafjallajökull in Iceland, but the majority of air traffic on the West Coast, other than the brief hiatus by Alaska (which was more for the health of ground crews than the planes themselves), has mostly continued as usual.
The other good news is that you don’t have to worry about smoke entering the cabin as you’re flying through it, even though you might smell it. “Cabin air is a roughly 50-50 mix of recirculated and outside air. The recirculated air passes through a highly-engineered filtration system, and turns over every few minutes,” said Frank. “Outside air particulates, such as smoke, that enter the cabin do get filtered out relatively quickly by the HEPA filters within a few rounds of recirculation.” (For what it’s worth, those filters can also effectively remove COVID-19 from the air, too—they’re the same type of filters used in hospitals.)
There is one case, however, in which planes won’t fly through smoke. Some of the most severe wildfires can produce a pyrocumulonimbus cloud, a thunderstorm that forms from the heat and smoke, which NASA refers to as a “fire-breathing dragon of clouds.” Those are a no-go for airplanes, but not because of the smoke itself: planes avoid all kinds of thunderstorms, including wildfire-induced ones, because the extremely turbulent atmospheric conditions could cause significant problems for the aircraft, its crew, and its passengers.