and How Airlines Overbook Flights
A sometimes unfairly condemned activity
that usually works to your advantage
The flipside of full
flights can be an increased chance of finding yourself with
no seat, due to the flight being oversold.
of a series on being bumped from flights, see the other
articles in this series listed on the right.
Airlines are experiencing
massively increased rates of involuntary denied boarding
compared to earlier this decade, while at the same time, the
proportion of passengers willing to voluntarily accept denied
boarding has plummeted.
While you're still
statistically unlikely to be involuntarily denied boarding, the
ugly industry trends towards fewer and fuller flights could make
the consequences of any such problem much harder for you to
This first part of our series
on what is commonly referred to as 'bumping' puts these issues
into their overall context.
Why Airlines Overbook Flights
Most airlines will overbook
their flights, sometimes by as much as 50%. This means
that if they have a 150 seat airplane, they might sell 225
tickets for that flight - a mix of all different fares.
They do this for two
Not everyone travels on their
Firstly, the airlines know that not
everyone who has booked to travel on any specific flight will
actually travel on that flight. Various reasons can mean
people don't show up for the flight. A person might arrive
at the airport early and fly out on an earlier flight.
A business traveler might
have made duplicate bookings on multiple flights so that he has
the certainty and flexibility to travel on whichever flight
becomes the most convenient for him. Someone else might
become sick and unable to travel. And some people might be
doing a 'back to back' itinerary and have no intention of
traveling on the ticket, even though they've booked and paid for
(Please see our article
series on Airfare Loopholes for
an explanation of back to back ticketing and other ways to beat
the airlines at their own games.)
So, for whatever reason,
airlines know that not every booking for any flight will result
in the person for sure turning up to travel. By keeping
careful historical records of past similar flights, and matching
it to all sorts of other variables including such things even as
the weather at the departure and arrival points, relevant
holidays, other flight cancellations, and all sort of things,
they have developed reasonably accurate forecasting models to
give guidelines for what percentage of travelers booked on a
flight will actually travel and what percentage will not travel.
This information allows them to accept a number of overbookings
with equanimity, and usually with few problems.
Selling more seats earns the
airline more money (of course)
The second reason the
airlines do this is simply to make more money.
airline can sell 225 tickets on a flight that uses a plane with
only 150 seats, obviously it stands to make more money than if
it restricts itself to selling only 150 tickets.
But this is not just a
selfish venal act on the part of the airlines that we should
decry. Read on...
Overbooking is a Good Thing
Now here's an interesting
concept to keep in mind. Sensible responsible overbooking
(assuming these are not conflicting concepts!) is a good thing,
because it enables the airline to accept lower fares for the
seats they are overbooking.
If an airline says to itself
'I need to earn $15,000 from this flight' and if it has 100
seats on the plane, it needs to get an average of $150 a ticket
if it sells 100 tickets. But if it says 'I'm going to
oversell the flight' and if it sells 150 tickets - ie, by
overselling the flight by 50% - it only needs to get an average
of $100 per ticket.
So overselling, if it is
done correctly (ie - as long as it doesn't result in passengers
not being able to take the flights they've booked and paid for), can help us all to get lower airfares, and
so is a
Overbooking can also be a
good thing if you can take advantage of an airline's request for
volunteers to accept being bumped off a flight in return for a
'bribe' - usually either a voucher good for some hundreds of
dollars off a future flight, or a free flight voucher.
Why Overbooking Sometimes Goes
No matter how exact and
scientific an airline's overbooking model is, there is still an
element of random chance, and an additional element of
impossible-to-anticipate other variables.
For example, an unexpected flight
disruption by another airline might suddenly cause a surge of
extra people seeking to travel on a flight, disrupting the
airline's careful projection. Weather cancellations and
other operational disruptions can also mess up an airline's
projections for passenger numbers.
And then, sometimes, an airline's
'run of luck' simply turns bad. Just like if you throw a pair of
dice enough times, every so often you'll get a double-six
appear; so too, if you bet on overbooking statistics enough
times, every so often, your bet will go wrong.
Furthermore, these days,
airlines are feeling the need to overbook more aggressively than
before, because they need as much money as possible per flight,
so they are choosing to reduce the safety margin and to overbook
in greater numbers, thereby of course increasing the risk that a flight might end
up with too many people turning up at the gate seeking to
How Often Does Overbooking Go
Surprisingly, it is fairly
easy to answer this question, and moderately exactly. The
Department of Transportation issues quarterly data showing the
number of passengers who both accept voluntary inducements to
not take the flight they were booked on, and the number of
passengers who are forced to take a later flight, whether they
wish to or not. You can see their latest reports
This information is of
course only as accurate as the reporting from the airlines, and
there are a number of 'exceptions' - cases where an airline not
accepting a passenger's booking doesn't formally count as an
overbooking denial. But the information is the best there
is and is definitely helpful.
For the period January -
March 2009 (the most recent quarter available at the time of
writing this article) you had the least chance of being
involuntarily denied boarding on a Jetblue flight (who bumped no
passengers at all against their will), and most chance of being
moved off your flight with Atlantic Southeast Airlines (who were
bumping 3.94 of every 10,000 passengers). American Eagle
and Comair were the two next worst offenders.
In round figures, and on
average, currently about 1.3 passengers per 10,000 passengers are denied
boarding against their wishes, and for every involuntary denied
boarding person, there are about nine other passengers who have
volunteered to be bumped, accepting some form of inducement in
the process from the airline.
of a series on being bumped from flights, see the other
articles in this series listed on the top right.
Related Articles, etc
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17 Jul 2009, last update
25 Aug 2018
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