Greg Lindsay knows a lot about airports: in fact he’s just written a whole book about them, called Aerotropolis. So I thought I’d ask him whether my uninformed ramblings about airports and infrastructure made any sense.

Specifically, I asked him about freight, which is where a huge amount of the real value in airports lies. How do freight airports compare to what we air passengers are used to? What’s their architecture like? Are the most modern and efficient freight airports just as beautiful, or even more so, than passenger airports, or are they just big ugly concrete sheds? How do they compare to the great resorts of America? (That one for Larry Summers.) And how important are they, from an infrastructure perspective?

He replied:

In many cases (especially overseas), the busiest cargo airports are also some of the busiest passenger hubs. Maybe the best example is Hong Kong, which cost $20 billion to build (still the most expensive ever) and boasts a passenger terminal which is both one of the nicest shopping malls and biggest buildings in the world. That’s what Larry Summers probably has in mind. But maybe more important is the airport’s cargo terminal, which is the second busiest in the world (after the FedEx hub in Memphis) and has all the ambience of the Port Authority Bus Terminal — it’s basically a giant loading dock hundred of feet tall. But you can’t have one without the other. The gleaming terminal isn’t a loss leader — it rakes in millions from duty free and other sources — and it attracts the passenger traffic which makes being a cargo hub possible. Eighty percent of the Apple iPods in the U.S. were made at the giant Foxconn plant in Shenzhen and flown to LAX in the bellies of Cathay Pacific passenger flights. Hong Kong’s airport is what makes it possible for Apple to manufacture nearly all of its products in a single factory on the other side of the world. So yes, sometimes it pays to have a gleaming airport.

I had one follow-up: How important is the “gleaming” bit? If Hong Kong’s new airport had all the atmosphere of Newark International, but still had the same capacity, what difference would that make? Here’s what I got back:

Bling doesn’t matter. Size matters. Speed and efficiency matter. Being able to move 50 million people a year in and out quickly and painlessly is the point. America’s airports can barely do that. Summers was wrong to compare airports and resorts; what makes Hong Kong’s or Beijing’s or Dubai’s super-sized terminals important is the fact that they’re super-efficient and haven’t outlived their lifespans by a good 20 years — not because they resemble a dragon or are filled with palm trees. Newark is a perfectly fine airport (the Continental piece of it, anyway), but an even better example is JetBlue’s Terminal 5 at JFK. It’s a big, cheap steel box with some nice restaurants and free WiFi inside, which distracts you from the fact that it was engineered to turn planes around in record time, which directly affects the airline’s bottom line. If all of our airports were that good, we’d be fine. And it cost a fraction of the airport resorts in Asia.

So I’m still not convinced that a major investment in airports is the best — or even a modestly good — use of federal infrastructure-investment funds. Yes, America’s airports are miserable places to travel through. But if what we want to do is boost long-term GDP, then there are better places for the government to spend its money. As and when airports get replaced and upgraded, they will naturally become more modern and efficient. Sadly, however, that’ll take time — and it might not make the passenger experience much better.