Driving vs Flying: Which Harms Our Planet Less?

Both cars and planes are awful polluters. But if you’re planning a trip and the less polluting alternatives — train or bus — aren’t options, which should you choose: driving or flying?

There are many considerations when traveling, including time, money, the number of people, and whether or not kids are involved. But if you’re deciding between traveling by car or by plane, based solely on environmental impact, which one is least harmful? We looked at two criteria for determining the better option: emissions and microplastic pollution from tire wear.

Emissions Refresher

Environmentalists have been worried about carbon emissions for years now — it’s why electric vehicles are so popular and why Google allows you to search for flights based on carbon emissions. But there’s more to emissions than just carbon, so here’s a quick refresher of the terms relevant to cars and planes.

• Greenhouse gas (GHG) refers to atmosphere-warming gases. NASA lists five as influential on anthropogenic (human-caused) global warming.   
• Carbon dioxide (CO2) is the most well-known greenhouse gas and the primary GHG emitted by human activities. It can last for centuries in the atmosphere.
• Methane (CH4): While its warming effects in the atmosphere last only about 20 years, this GHG is up to 80 times more powerful at trapping heat than CO2.
• Carbon dioxide equivalent (CO2-eq or CO2e): This refers to the number of metric tons of carbon dioxide equal to 1 metric ton of another greenhouse gas in warming capability. This calculation is what we use to compare primarily CO2-emitting cars (99% CO2) to multiple GHG-emitting planes (CO2, CH4, and more).

The travel method that produces the least emissions in this race will be determined by CO2/CO2-eq per passenger.

Driving vs Flying Emissions

Our data will focus on averages, but the equations and sources below will show you how to figure out calculations for your own trip.

For car emissions, we’ll use the US fuel economy calculator, which you can use for your planning. For plane emissions, we’ll use Google’s flight emissions calculator as listed on its booking search. However, a plane’s carbon emissions account for only about one-third of its total emissions, and Google recently neutered its flight calculator to calculate only CO2 and ignore other GHG. Because of the recent change, the UK government recommends multiplying Google’s flight emissions data by 1.9 to determine the total emissions of a flight — this is a long-agreed-to multiplier to assess total emissions. Most travel sites also list Google’s emissions data.

Factors that we consider in this comparison include the number of people traveling, type of vehicle, and distance of travel (short trips vs long trips). Google also accounts for the size and type of aircraft in its data. Lastly, regular unleaded fuel is used in this comparison.

Car and Trip Comparisons

We’ve picked two cars and two trips to compare driving vs. flying. Gas guzzler and fuel-efficient, long and short distances. The cars and their emissions are:

• 2021 Honda Insight Hybrid. It gets 52 miles per gallon city and highway combined and emits 170 grams of CO2 per mile.
• 2020 GMC Yukon 4WD. It gets 17 miles per gallon city and highway combined and emits 525 grams of CO2 per mile.

The two trips are:

• Los Angeles to New York City: Google Maps says it is 2,789.3 miles on a preferred route through the upper Midwest and takes 42 hours of continuous driving, so not exactly realistic, but a good benchmark.
• Minneapolis to Milwaukee: It is 336.5 miles and takes a little over five hours to drive.

Emissions Results of Flying vs Driving

For our flying trips, we picked nonstop direct and the lowest emissions option. This is the minimum, best-case scenario for flying.

We’ll also multiply Google’s stated emissions by 1.9 to get the flight’s CO2e. The data listed are per passenger, which decreases as the number of car passengers increases.

For flights, the number of passengers doesn’t change the results because the data are already listed per passenger. However, while flight emissions per passenger stay the same, the total amount of emissions increases for every person added.

LA to NYC

For this trip, we’re using a nonstop Spirit Airlines flight that takes a little over five hours.

Minneapolis to Milwaukee

For this trip, we’re using a nonstop Delta flight that takes 1 hour and 27 minutes.

As you can see, from an emissions perspective, flying is almost always the more environmentally damaging option.

Wildcard: Tire Pollution

Tires are one of the main sources of microplastics found in the ocean, and it would be irresponsible to compare the environmental effects of driving and flying while focusing only on GHG emissions. Microplastics are now found on newly formed volcanic beaches, at the top of mountains, and in human breast milk. While we are not fully aware of all the damage microplastics do, we know that they lead to both ocean acidification and biodiversity loss through toxin leaching.

These days, tires are made primarily from synthetic plastics rather than rubber, and microplastics are created from friction between roads and tires. Planes contribute only 2% of global tire microplastic pollution, with cars creating the majority. Microplastics range in size between 5 millimeters and 1 micrometer, and they move with the winds and the oceans.

We are comparing toxic gases and toxic solid objects here, which is a little like comparing poisonous apples with poisonous oranges. It doesn’t work. But at the same time, this discussion would be lacking if microplastics weren’t mentioned. Our planet is interconnected, and climate change is not a problem alone on an island. Biodiversity loss, ocean acidification — these things all go together.

So, Which Should You Use, a Plane or a Car?

As you can see, both are damaging in their own ways. For short-haul trips covered in a day or less, cars are preferable. But for the long haul as a solo traveler, planes are more efficient.

And regarding the microplastic problem, companies are working on plastic-free and low-plastic alternatives. There are almost plastic-free tires and plastic-free rubber options. But to butcher a Mark Twain quote, the difference between plastic-free and almost plastic-free is the difference between lightning and the lightning bug.

The best thing you can do though is talk about this during your planning, and use some of the tools mentioned in this article. When you talk and share your thoughts about these things, the effects can be exponential. Because our planet will be here for a long time — whether or not it’s livable for us, that’s another question.