Attention Passengers: Your Next Flight Will Likely Arrive Early. Here’s Why.
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Operations Nov 6, 2018

Attention Passengers: Your Next Flight Will Likely Arrive Early. Here’s Why.

The reason has less to do with planes and airport logistics than a strategic move by airlines.

Arrivals board at the airport.

Lisa Röper

Based on the research of

Dennis J. Zhang

Yuval Salant

Jan A. Van Mieghem

As frequent fliers, Kellogg’s Jan Van Mieghem and Yuval Salant have seen the same scene unfold numerous times: Their plane touches down and the pilot announces over the loudspeaker that the flight arrived ahead of schedule. Upon hearing about this stroke of good luck, the passengers immediately perk up.

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Every­body is smil­ing,” says Van Mieghem.

But are these smiles due to more than good luck? Van Mieghem, the Stu­art pro­fes­sor of man­age­r­i­al eco­nom­ics and oper­a­tions, and Salant, an asso­ciate pro­fes­sor of man­age­r­i­al eco­nom­ics and deci­sion sci­ences, began to won­der whether air­lines were strate­gi­cal­ly adjust­ing their sched­ules to make ear­ly arrivals more like­ly.

In a new study with Assis­tant Pro­fes­sor Den­nis Zhang of Wash­ing­ton Uni­ver­si­ty in St. Louis, the researchers ana­lyze two decades of data on 43 mil­lion domes­tic U.S. flights. They dis­cov­er that pub­lished flight times — the flight dura­tion that con­sumers see when they shop for plane tick­ets — increased 8.1 per­cent between 1997 and 2017, amount­ing to an addi­tion­al 341 mil­lion pas­sen­ger hours.

But when the researchers break down what caused that increase, they find that planes are not fly­ing slow­er than they used to.

Rather, near­ly half of the addi­tion­al time comes from air­lines strate­gi­cal­ly padding their sched­ules. Late planes are bad for busi­ness — so, by adding time to their pre­dict­ed flight lengths, air­lines can increase the odds that their planes will arrive on time. This sched­ule padding is espe­cial­ly com­mon on flight routes with less com­pe­ti­tion, the researchers find. 

In Search of Lost Time

The team looked at his­tor­i­cal data from the Bureau of Trans­porta­tion Sta­tis­tics con­tain­ing detailed data on 43 mil­lion flights over the last 21 years. They ana­lyzed changes in flight dura­tion for the same route oper­at­ed by the same car­ri­er year over year.

On paper, it appeared that the same flights now take sig­nif­i­cant­ly longer than they did in the 90s.

The researchers knew that there were sev­er­al pos­si­ble expla­na­tions for this. Planes may be spend­ing more time cir­cling in the air wait­ing for an open land­ing strip, or more time on the ground wait­ing for a gate to become avail­able. Anoth­er pos­si­bil­i­ty is that air trav­el has become less pre­dictable — if so, air­lines could be adding more buffer time to guard against increas­ing­ly fre­quent delays from bad weath­er or oth­er unplanned events.

A final pos­si­bil­i­ty was strate­gic padding”: air­lines might extend their sched­uled flight times not for any logis­ti­cal rea­son, but as a mat­ter of sheer busi­ness strat­e­gy.

When flights arrive on time or ahead of sched­ule, you get hap­py cus­tomers,” says Van Mieghem.

How­ev­er, Salant notes, there are costs asso­ci­at­ed with that.” For one, if an air­line pads too much, a com­peti­tor can under­cut them by offer­ing a short­er flight. Fur­ther­more, flight crew mem­bers are often paid for the full sched­uled flight dura­tion, regard­less of how long the flight actu­al­ly takes.

The researchers cre­at­ed a math­e­mat­i­cal mod­el to tease out how much each fac­tor — air time, ground time, unpre­dictabil­i­ty, and strate­gic padding — con­tributed to the increase in pub­lished flight times.

They found that planes spend rough­ly the same amount of time in the air as they did 21 years ago. And unpre­dictabil­i­ty did not seem to be play­ing much of a role in the increase, either.

Ground time was a dif­fer­ent sto­ry. Pas­sen­gers were spend­ing more time on the plane wait­ing for take-off, or wait­ing for a gate after land­ing, pos­si­bly because of increased air traf­fic,” Salant says.

But that increase in ground time explained about half of the increase in pub­lished flight times, leav­ing more than 150 mil­lion pas­sen­ger hours unac­count­ed for. The researchers con­clud­ed that this remain­ing time was the result of strate­gic padding.

We find that the miss­ing time is not due to phys­i­cal con­straints like air time and ground time or vari­abil­i­ty. It’s due to strate­gic deci­sion-mak­ing by air­lines. They’re padding their sched­ules, and they’re doing it for a reason.”

— Jan Van Mieghem

Less Com­pe­ti­tion Means Longer Flight Times

Why has strate­gic padding become more com­mon? The researchers sus­pect­ed that part of the rea­son is dwin­dling com­pe­ti­tion.

If you have plen­ty of com­peti­tors, log­ic dic­tates that you will seek to offer cus­tomers the most effi­cient route from A to B. You’ll cut back your sched­uled flight time,” Van Mieghem explains.

But due to bank­rupt­cies and merg­ers, there are few­er large U.S. air­lines today than in 1997. So air­lines today may feel less com­pet­i­tive pres­sure to offer short­er flight times.

To test this the­o­ry, the researchers looked at how pub­lished flight times changed after com­peti­tors either start­ed or stopped offer­ing flights on a par­tic­u­lar route.

As pre­dict­ed, when com­pe­ti­tion grew stiffer, air­lines cut down trav­el time. Con­verse­ly, Van Mieghem says, as the play­ing field thins out, less com­pe­ti­tion makes it eas­i­er for air­lines to do the opposite.

A Sil­ver Lin­ing to Sched­ule Padding?

Walk around O’Hare air­port, for exam­ple, and you are like­ly to come across a bill­board adver­tis­ing the reli­a­bil­i­ty” of Unit­ed Air­lines’ flights.

But it’s not real­ly about reli­a­bil­i­ty,” Van Mieghem says. If air­lines real­ly want­ed to improve reli­a­bil­i­ty, they’d focus their efforts on enhanc­ing their oper­a­tions. What our study shows is that this is not the case. What they’re going for instead is the eas­i­er — and cheap­er — option of sched­ule padding.”

Nonethe­less, the researchers stress that sched­ule padding has its ben­e­fits. After all, a flight that usu­al­ly takes 90 min­utes may indeed take 120 on an unlucky day. By pub­lish­ing a time clos­er to two hours, the researchers explain, air­lines are sim­ply erring more on the side of cau­tion.

In fact, sched­ule padding may actu­al­ly help trav­el go more smooth­ly. Pas­sen­gers are not only more like­ly to expe­ri­ence the joy of an on-time arrival, but also get more buffer time to make a con­nect­ing flight.

And the paper’s rev­e­la­tions sug­gest that there is an oppor­tu­ni­ty for pas­sen­gers to be strate­gic, too, says Van Mieghem.

We tend to allow a lit­tle extra time for delays or hold-ups when we’re trav­el­ling,” he notes. But if con­sumers know that their flight is like­ly to get in on time, they might save time by reduc­ing that buffer in their sched­ule. Of course,” he adds, this is a ques­tion of our indi­vid­ual tol­er­ance for risk.”

Featured Faculty

Yuval Salant

Associate Professor of Managerial Economics & Decision Sciences

Jan A. Van Mieghem

Harold L. Stuart Distinguished Professor of Managerial Economics, Professor of Operations

About the Writer

Áine Doris is a freelance writer and editor based in London and Barcelona.

About the Research

Zhang, Dennis J., Yuval Salant, and Jan A. Van Mieghem. 2018. “Where Did the Time Go? On the Increase in Airline Schedule Padding over 21 Years.” Working paper.

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