Ask the pilot

Remember the sense of awe you used to feel on an airplane ride? Where did it go? Plus: The lowdown on that "filthy" and "germ-laden" cabin air.

Published March 9, 2007 12:40PM (EST)

If the feedback from my last two columns has taught us anything, it's that people really, really don't like to fly. With that on the table, try to imagine the following:

You wake up early for the 45-minute subway ride to Logan International Airport in Boston. The shuttle bus brings you to Terminal C, where you stand in line to be frisked and X-rayed before reaching an overcrowded departure lounge. Half an hour later your flight pushes back, languishes in a taxiway queue for several minutes, then finally takes off. So far this is nothing exceptional, but here's the twist: The plane's scheduled destination is, well, Boston. The jet never climbs to more than 10,000 feet. It makes a lazy circuit above the North Shore coastline, swings eastward toward Cape Cod, then circles west in the direction of Logan. Fifteen minutes later, the landing gear clunks into place, and just like that you're back where you started. You disembark, with smiles and handshakes all around, head for the shuttle bus, and take the subway home again.

To most of you that doesn't sound like a terribly fun morning, but what if I told you that once upon a time, not only did thousands of people willingly endure this, but they actually paid for the privilege? It was the late 1970s, and I was one of those people.

The flights were yearly fundraisers, hosted by different carriers on behalf of local charities. In '78, I remember, it was the Boy Scouts of America. A year later it was the Jimmy Fund, an organization dedicated to pediatric cancer research (and best known for its partnership with the Boston Red Sox baseball team). People paid 10 or 15 bucks for a ticket. Flights left hourly, all day long, with each ride lasting about 25 minutes. For the airlines, maybe, it was an IRS write-off, but the crews worked for free.

At the time I was 13, maybe 14 years old, but this wasn't just for schoolchildren. My friends and I, along with many of our parents and teachers, spent weeks looking forward to it. On board, the crowd would be a mix of first-time fliers, airplane buffs and regular people looking for an unusual way to spend their Saturday.

I did it three times. The first, in 1978, was on board an Air New England FH-227, a 50-seat turboprop. I still have several photographs, snapped through one of the plane's giant, 19-inch oval windows, showing snaky brown marshlands and the contours of Revere Beach from 5,000 feet. (My camera was a brown Kodak Instamatic no bigger than a deck of cards. I took so many adolescent airplane pics with the damn little camera that I can vividly recall the feel of its thumb-driven film winder.) Seated just aft of the plane's high-mounted wing, I remember the sight of the landing gear folding backward into the engine nacelle and the puff of white smoke on touchdown.

Next it was a TWA Boeing 707. That was a Jimmy Fund flight, and my first and only ride in a 707. While aloft, passengers stood in the aisle and were escorted, two at a time, onto the flight deck.

And the last one -- I'm thinking 1980 -- was with Eastern Airlines on an Airbus A300. Together with four friends, I splurged for two flights that day, one in the morning and one in the afternoon, at $10 apiece. That's what we did with our Christmas money. Eastern was the first U.S. carrier to fly the wide-body A300, which had two seats on either side and four across the center. We pressed to the front of the line in order to snag windows. By the time they closed the doors, every seat on that plane, middle rows and all, was taken. A popular local disc jockey sat in one of the cockpit jump seats, broadcasting live during takeoff and landing. On touchdown, everybody clapped.

Much has changed in a quarter-century. For one, all three of those carriers are gone now: TWA into American; Eastern into Frank Lorenzo's toilet; Air New England, whose planes were once as common around here as pigeons, into some obscure oblivion that even I can't remember. And the entire premise, of course -- shelling out cash for a flight to nowhere, and actually being excited about it -- will strike most people as ludicrous.

A form of these flights still exists, albeit not marketed to the average citizen, and for considerably steeper fares. In Europe, agencies arrange trips for airplane junkies, who pay hundreds of dollars to experience a round-robin journey aboard this or that unusual airliner. But what's missing is the public's sense of awe, the shared thrill of going for an airplane ride.

Where it went, of course, both for better and for worse, is into the maw of deregulated skies. Jimmy Carter put his name to the Airline Deregulation Act of 1978, and shortly thereafter these charity junkets began disappearing. Airlines were no longer willing to volunteer their employees or equipment, and it wouldn't be long before passengers themselves, flying in ever-greater numbers, no longer savored the thrill. In came cutthroat competition and cheap tickets, out went the novelty of flying. The first-time flier is today a rare bird, the enthusiastic flier all but extinct.

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Q: Could you clear the air, as it were, regarding one of the most common water-cooler topics pertaining to flying: the quality of cabin air. We hear lots of anecdotal talk about how filthy and germ-laden it is.

"Filthy" and "germ-laden" are two of the milder descriptors used in popular reference to cabin air. A scan through some of my letters reveals these as well, used alone or, more commonly, in a long, multi-adjective chain: rotten, disgusting, wretched, skanky, rancid, putrid, fetid and fart-filled. And legion are the accounts of travelers allegedly made deathly ill by microscopic pathogens circulating through a plane. There is also the notion, similar to the myth about reducing the amount of oxygen, tackled here a couple of weeks ago, that crew members tinker with airflow in efforts to save fuel. But despite what people think, and despite the lies and nonsense put forth by "advocates" like Diana Fairechild (almost nothing on this page, for example, is accurate), the air is surprisingly clean and fresh.

On all modern aircraft, passengers and crew breathe a mixture of fresh and recirculated air. Using this combination, rather than fresh air only, makes it easier to regulate temperature and helps maintain a bit of humidity (more on the latter in a moment). The supply is bled from the compressor sections of the engines. Compressed air is very hot, but the compressors only compress; there is no contact with fuel, oil or combustion gasses. From there, it is plumbed into air-conditioning units, known to pilots as "packs," for cooling as needed. It's then ducted into the cabin through louvers, vents and the eyeball gaspers above your seat.

The air circulates through the cabin until eventually it is drawn into the lower fuselage, where about 50 percent is vented overboard -- sucked out, if you will, by the pressurization outflow valve. The remaining portion is run through filters, then remixed with a fresh supply from the engines, and the cycle begins again.

Among those adjectives already listed, people are known to describe jetliner cabins as "stagnant." It can seem this way at the gate or while taxiing, but during flight the air is constantly in motion. (The flow is front to back, so if you're especially germophobic, try sitting in a forward row.)

The air is also a lot healthier than people give it credit for, though it somewhat depends on the aircraft model and, as you'd expect, how full it is. Studies have shown that a crowded airplane is no more germ-laden than most other enclosed spaces, and usually less so. Those underfloor filters are described by manufacturers as being of "hospital quality." I needn't be reminded that hospitals are notorious viral incubators and ideal places to get sick, but according to Boeing, between 94 and 99.9 percent of the airborne microbes are captured, and there's a total changeover of air every two to three minutes -- far more frequently than occurs in buildings, where the percentage of fresh air is also much lower. (Personally, only once do I blame a particular illness on something I picked up while flying -- it was a Continental flight from Frankfurt, Germany, to Newark, N.J., in 1995 -- and even then I can't be sure. By contrast, as both a youngster and an adult, I've been struck by classroom contagions many times.)

The strength of airflow is not always directly adjustable. Cockpit controls vary, and sometimes allow only for basic on/off positioning, along with some emergency shutoff options. Flow is regulated separately from each engine, but the switches are typically left at some standard setting and the system more or less takes care of itself. On the flight deck of the Airbus A320, one of the most common types, there's a "Pack Flow" switch on the overhead panel with three positions: Lo, Norm and Hi. At one airline, guidance is to use Norm unless fewer than a hundred passengers are on board, in which case Lo is selected.

Temperature, meanwhile, is controlled by separate switches, and can be fine-tuned as required.

Alas, with flow and circulation so dependent on engine power and pressurization, maintaining a comfortable environment on the ground is a lot more challenging than while aloft, especially on broiling tarmacs in the summer. "Stagnant": sometimes, yes. One or more engines are sometimes shut down during taxi, while at the gate it's usually the less powerful auxiliary power unit doing the work. (At some stations, external hoses are attached, supplying cold or hot air directly from the terminal or a portable air-conditioning unit.) Some aircraft have more effective packs, fans and gaspers than others, but I'm as mystified as you are as to why plane makers haven't engineered air-conditioning systems with a little more on-the-ground gusto.

Another common complaint is about dryness. Indeed, the air aboard commercial aircraft is exceptionally dry and dehydrating. The typical humidity level aboard a jetliner is around 12 percent. That's substantially drier than you will find in most deserts. This is chiefly a byproduct of cruising at high altitudes, where moisture content is somewhere between very low and nonexistent. That compressed, high-pressure bleed air from the engines also contributes. Humidifying a cabin would seem a simple and sensible solution, but it's avoided for different reasons.

First, to amply humidify a jetliner would take large quantities of water, which is heavy and therefore expensive to carry around. And because a portion of cabin air is constantly refreshed, humidifying systems would need to recapture and recirculate as much water as possible. Thus they'd be expensive, heavy and complicated. They do exist: One sells for more than $100,000 per unit and only increases humidity by a small margin overall. (Some aircraft have cockpit humidifiers, which, I'm told by pilots who have used them, are at best minimally effective.)

There's also the very important issue of corrosion. Dampness and condensation leaching into the structure of an airframe is never helpful.

If it's any consolation, the dryness, while irritating, actually helps keep the air clean. Bacteria, fungi and mold are able to spread and breed more readily in moist air. Although it can irritate your skin and nasal passages, you're better off with dry, cleaner air than damp and more germy air. The sensible tactic, obviously, is to drink lots of water (assuming you can find a crew willing to dispense it, or you're able to sneak some past the TSA scarecrows).

For those of you still skeptical, the new Boeing 787, set to debut next year, should make you happier. The 787 will have the cleanest air of any plane in existence, approximating the same microbial content of outside air, thanks to filters with an efficiency of 99.97 percent, and humidity will be substantially higher. The plane's all-composite structure will be less susceptible to condensation, and it will also be equipped with a complex circulation system that pumps dry air through the lining between the cabin and exterior skin, keeping out the moisture. Cabin pressure will be at approximately 6,000 feet during cruise, compared with the 8,000 feet standard, meaning more oxygen and less fatigue.

Until then, if you're the type who likes to fret over exaggerated dangers, forget microbes for a minute and consider microroentgens. As maybe you've read or heard, airline passengers are routinely exposed to increased levels of cosmic radiation. This is especially true in daylight hours at extreme latitudes, such as on transpolar routes, where natural atmospheric shielding is low. Add in those unpredictable solar flares, and radiation levels can approach or exceed those of a chest X-ray over the course of a single flight.

The risks this poses do exist, but they are small. On average, the hundred-thousand-mile frequent flier (or airline crew member) will receive a higher annual dose of radiation than a member of the general public, but exposure is well within the limitations normally set for nuclear workers and other industry specialists. The Europeans have been studying the issue closely, mandating that radiation levels be assessed and monitored for some crew members. One carrier, Scandinavian Airlines System, previously explored a connection between radiation and rates of crew-member cancer, but concluded there were no substantive links.

For an added thrill, do what I did, and combine your next high-latitude crossing with a day trip to Chernobyl.

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Do you have questions for Salon's aviation expert? Send them to AskThePilot and look for answers in a future column.

By Patrick Smith

Patrick Smith is an airline pilot.

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