The following appeared in the November 14, 2006 issue of THE NEW YORK TIMES:
LOADING AN AIRLINER IS
ROCKET SCIENCE
BY PAUL BURNHAM FINNEY
Airlines have been boarding passengers for decades, long enough, it would seem, to have figured out the best way to get people on and off a
plane. But they haven’t.
Midwest, Spirit and Virgin Atlantic. (Nearly all
airlines allow first-class or business-class passengers, and those with special needs, to board
first.)
Spurred by financial pressures and packed
planes — often 80 to 90 percent full — airlines
have come up with a wide variation of boarding
techniques, from the simple back-to-front protocol to one of the most complicated strategies,
known as the reverse pyramid system, that US
Airways has adopted. In September, JetBlue told
customers they could be seated first if they
booked Rows 20 to 26, the very back of the
plane.
Mathematicians would revel in the intricacies of
the new boarding techniques. There is the outside-in technique, nicknamed Wilma, for window first, then middle and then aisle, a technique favored by Delta and United. And there is
the sort of nonsystem system pioneered by
Southwest Airlines in which passengers board
in the order they arrive, with no assigned seats.
Minimizing time on the ground, especially on
shorter flights that use single-aisle aircraft,
means the planes can get back in the air faster so
they can make money. Even a few extra minutes
on the ground can throw off the day’s schedule.
“The advantage of a fast turnaround is not cutting costs but generating revenue,” said David
Swierenga, an economist and president of AeroEcon, an aviation consultancy. “If you save
time with each turn of, say, seven flights, you
may be able to schedule an eighth flight.”
Richard Aboulafia, an analyst at the Teal Group,
an aviation industry consultant, said the time
savings on transcontinental flights do not make
much difference. “But if it’s Baltimore to Islip on
Long Island, it matters.”
The basic back-to-front procedure is probably
the most familiar, and it is still used by many
airlines, including Air Canada, Alaska, American, British Airways, Continental, Frontier,
Among the reformers, US Airways can lay claim
to one of the most complex procedures. It is basically Wilma, with seats filled in a pattern as intricate as a microchip’s circuitry: rear window
and middle first, front window and middle next,
followed by rear aisle, then front aisle. The airline calls it the reverse pyramid system, but it
might be better described as a V-shaped sequence that operates by zones.
US Airways inherited that system from its newly merged partner, America West, which devised it back in 2002 with the help of an industrial engineering team at Arizona State University. Aided by photos taken at Los Angeles International Airport, the researchers created mathematical models and simulations using “pixels
as people,” as a team member, Menkes van den
Briel, puts it.
US Airways now uses the procedure on about
half of its Airbus A320 and Boeing 757 jets and
plans to finish the conversion next year. The
goal, as the Arizona State team’s report defines
it, is “to minimize the total expected number of
seat and aisle interferences.” So far, the system
has cut US Airways’ turnaround time by two to
five minutes, said a spokeswoman, Valerie
Wunder.
ple have an innate capacity to “self-organize”
and keep out of each other’s way.
Because behavior is so hard to predict, some argue that changing boarding procedures is less
effective than other tactics, like limiting carry-on
baggage.
AirTran Airways, a discount carrier, uses a simpler variation. “We divide the plane into six different sections in a rotating zone system,” a
spokeswoman, Judy Graham-Weaver, said.
Business class fills up first, along with specialneeds passengers. Then the airline begins the
seating sequence with the back five rows called
first, the front five behind business class second,
the next back five rows third — continuing until
the rows meet in the middle.
“To simplify and improve boarding, the only
way is to limit the amount of carry-on baggage,”
said Patricia A. Friend, president of the Association of Flight Attendants. “As long as people
hold up the boarding process — stowing as
much as they can get away with — it’s going to
be slow boarding and even slower deplaning.”
The recent security crackdown that tightened
limits on carry-on luggage serendipitously
proved her point. Some airlines said boarding
had become noticeably easier because many carry-ons ended up as checked baggage.
What is the advantage? One zone is stowing
bags while the next zone some distance away is
getting settled — and the zones tend not to interfere with one another, Ms. Graham-Weaver
said.
Perhaps the simplest approach is the open seating plan famously practiced by Southwest Airlines since its earliest days in 1971. It may seem
slightly quaint next to its more elaborate cousins, but it has helped make Southwest a turnaround champion that claims to take only 25
minutes on average to unload, clean and reload
its 137-passenger Boeing 737s.
The variable that keeps upsetting the airline industry’s careful planning is the unpredictability
of human behavior. The industry calls it “interference,” and it means time-killing activities like
elderly passengers perching on armrests to stuff
a bag into the overhead bin.
“That’s very fast,” said Mr. Swierenga, the consultant, adding that there are no industry
benchmarks on turnaround time. “It depends on
the size of the aircraft,” he said. “A 747 jumbo
can take hours.”
“The unexpected behavior of passengers can
lead you to chaos theory for an explanation,”
Mr. Aboulafia said. “That’s when random
events set off a sequence of unpredictable actions and your best-laid plans go out the window.” But some boarding experts note that peo-
Southwest’s turnaround time is “below those of
our competitors,” said a Southwest spokeswom-
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an, Beth Harbin, who added that the range is 35
minutes to an hour for most airlines.
book at the last minute without losing out on a
good seat,” said Ms. Harbin, the Southwest
spokeswoman. “But after going electronic with
boarding passes, we cleared at least the technology hurdle of how to assign seats.” Southwest is
adamant about not altering its boarding system
until at least 2008.
Southwest’s system is also cheap and uncomplicated, requiring almost no exotic technology.
Customers get assigned to Groups A, B or C on
their boarding passes, in the order in which the
passenger checks in. Groups are called in alphabetical order, with passengers rushing to occupy
the seat of their
choice.
Northwest, which has traditional assigned seating,
recently
replaced
its
back-to-front
loading
with
Southwest-style
open boarding.
Some corporate
travel managers
have
complained
that
their fliers are
getting
the
Southwest
open-seating
treatment even
though they are
paying full fare.
But Northwest,
like most major airlines, provides a separate
boarding lane for elite business travelers, even
when they are late to the gate. And it says its
system reduces boarding time by seven minutes.
Though some
Southwest passengers liken it
to a cattle car,
they are generally
good
sports. But in
blogs and other forums they
grouse
that
they have to be
at the airport
early to get the
best seats.
To show off
the effectiveness of its simple system, Southwest’s scheduling department has come up with a what-if
model, in which turnarounds take five minutes
longer. To keep its current schedules of 2,773
daily turns for its fleet of 461 737s, the airline
would need 18 additional aircraft costing a total
of $972 million — not including the cost of crews
and maintenance workers.
So which boarding technique works best? There
are skeptics who scoff at all the hand-wringing
and research experiments and contend that all
these attempts at saving time are a waste of
time.
Southwest has quietly done tests of so-called
dual jet bridges in Austin and Dallas to accelerate boarding by loading passengers through two
doors at once. But the bridges proved to be unreliable. The airline does use a different kind of
dual bridge in Albany, but has found it only
marginally better than single bridges.
“The airlines are looking for a new time-saving
idea they can believe in and reduce it to a computer code,” said Robert W. Mann, an aviation
consultant in Port Washington, N.Y. “Just say,
‘It’s time to go’ and random boarding will get
the same result as any systematization.”
Last summer Southwest began experimenting
with assigned seating, Wilma-style boarding
and other loading methods on flights out of San
Diego because of the variety of short, medium
and long-haul flights there.
So far, passengers polled by Southwest are evenly divided between leaving open-seating alone
or changing it. “Our fliers are passionate about
what they like — for instance, the fact they can
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