1 Billion air travels coming soon

Climate change, what climate change?

This is another guest post by Drew Erskine. He predicts when we hit 1 billion air travels and makes the point that Briefed by Data has been making: there is not evidence we’ll reduce energy consumption, in particular, fossil fuels. Enjoy his post. Cheers, Tom

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Every year, headlines such as “Record-Breaking Holiday Travel This Year” or “TSA Breaks Holiday Traveler Record” appear. Observing the aftermath of COVID-19, I couldn't resist the thought: shouldn't we be striving to reduce our carbon footprint? As I delved into TSA's Travel Numbers report, I realized we are approaching a significant milestone: 1 billion travelers in a single year (Figure 1). This report gives us all travelers that go through TSA at any given airport in the United States (though it’s not clear if these include the 15 checkpoints outside of the United States).

Figure 1. Data from the TSA.

Naturally, the first question that came to mind was: How long will it take to reach the 1 billion milestone? Answering this wasn’t easy, as TSA only provides data going back to early 2019, significantly limiting the assumptions I can base a forecast on. I even filed a Freedom of Information Act request with the Department of Homeland Security to access older data. However, it's likely that searching through historical archives is not at the forefront of your priorities when you are occupied with “breaking records.”

To get a better idea of future trends in traveler checkpoint numbers, I used two different forecasting methods: linear regression and logarithmic regression. Each one gives a unique way of looking at how checkpoint numbers might grow in the coming years. With linear regression, I focused on weekly checkpoint numbers that reached at least 90% of 2019 levels, as I considered this threshold a reasonable indicator of returning to normal travel activity. Using those weekly numbers, I then create a best fit line to tell us more about future weeks. I calculated monthly totals, which then added up to an annual forecast seen in Figure 2.

Figure 2. Data from the TSA.

The logarithmic regression is a bit more advanced but offers another perspective. After COVID, checkpoint growth didn’t happen at a constant rate—it started off strong but slowed down over time, forming a curve that looks a lot like a logarithmic shape. In mathematics, we can create a function that best fits this pattern just like we did with a linear regression, allowing us to generate a trendline that extends into the future. Figure 3 illustrates this calculation compared to our linear regression.

Figure 3. Data from the TSA.

Looking at the results of these two approaches, as long as nothing major, like another pandemic disrupting travel, the linear regression suggests we will reach 1 billion in 2028, while the logarithmic regression predicts it will happen sooner, in 2027. For this year, I estimate checkpoint volumes will end up around 912 million travelers, falling about 90 million short of the big milestone.

Remember how we started with weekly data? Well, we can zoom in by day and make daily predictions using historical daily distribution, helping pinpoint the exact dates we might hit 1 billion travelers. The linear regression suggests a date of December 30, 2028, with a margin of error of approximately one week, whereas the logarithmic regression suggests an earlier date of December 29, 2026, with a similar margin of about seven days. Figure 4 shows both forecasts and how the daily trends play out.

Figure 4. Data from the TSA.

Math aside, this is clearly not the direction we want to be going if we are serious about climate change. In a Nature article and also talked about in a Briefed by Data post called “CO2 emissions of traveling," in 2022, during a time where we were still recovering from COVID, the transport sector accounted for 30% of global energy use and 37% of global carbon dioxide emissions. Despite its large share in national emissions, transport has been one of the most difficult sectors to decarbonize. Well, at an average of 250 passengers on commercial flights at 1 billion checkpoints in a year, that is 4 million flights a year or 11,000 flights a day! How hard could it be to cut back the number of flights by at least 5%? All this to say, we are clearly more set on affordability and profitability than on our carbon footprint.

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