If you happen to be flying through tiny Idaho Falls Regional Airport, you’ll be treated to Wi-Fi download speeds averaging more than 200 Mbps, faster than most people enjoy from their home Wi-Fi and more than enough to support such data-intensive activities as downloading and streaming movies. That’s according to tests conducted by Ookla, included in a new study of airport Wi-Fi speeds.

On the other hand, average Wi-Fi speeds at the nation’s largest airports are sometimes so slow that you’d be hard pressed to do anything more than check email. Download speeds at Atlanta airport, for example, averaged a dismal 2.71 Mbps. At the other extreme, Wi-Fi users at Denver International can stream high-definition movies at a brisk 61.74 Mbps, the fastest rate of any of the 20 largest U.S. airports.

In other words, your Wi-Fi experience may vary from airport to airport. A lot.

Here are the 20 largest U.S. airports ranked according to the average speeds of their public Wi-Fi networks, from fastest to slowest:

1. Denver
2. Philadelphia
3. Seattle-Tacoma
4. Dallas-Ft. Worth
5. Miami
6. LaGuardia
7. Chicago O’Hare
8. Newark Liberty
9. New York-JFK
10. Houston
11. Detroit Metropolitan
12. Los Angeles International
13. Charlotte Douglas
14. Boston Logan
15. Phoenix
16. Minneapolis-St. Paul
17. Las Vegas
18. San Francisco
19. Orlando
20. Atlanta

Wi-Fi Versus Cellular

Unless you have an unlimited data plan from your cellular carrier, you’ll most likely first try to connect to the Internet via an airport’s Wi-Fi before resorting to your limited cellular data plan. As it turns out, that may not be the best option if a fast connection is the priority.

The report compared the public Wi-Fi speeds with cellular speeds at the 20 largest airports, and the results were decidedly mixed. At nine airports, the public Wi-Fi was faster than the available cellular download speeds. And at 11 airports, cell speeds were faster.

So if you’re stuck waiting for a connecting flight in Atlanta, rather than suffer through 2.71 Mbps downloads via the airport’s Wi-Fi, switch over to your provider’s cellular service, which is almost 10 times faster, averaging more than 20 Mbps.

And wherever you happen to be, it’s worth comparing Wi-Fi and cellular speeds, to see which is faster. The differences can be significant.

Reader Reality Check

Was your strategy for getting a fast Internet connection when on the road?

After 20 years working in the travel industry, and almost that long writing about it, Tim Winship knows a thing or two about travel. Follow him on Twitter @twinship.

This article first appeared on SmarterTravel.com, where Tim is Editor-at-Large.