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THE STORY OF THE "GARAGE-O-MIZER"

Bill
Employee
Employee
If you were to ask me how we write the Southwest Airlines flight schedule, my answer would be much different today than it was just a few years ago.  When I joined Southwest in 1990, we had just over 100 airplanes, a little over 1,000 flights a day, and about eight to nine weeks to analyze and re-write our airlines schedule by hand;which we did five times a year.   Fast forward to 1999.  By that point, we had grown to nearly 300 airplanes, over 2,400 flights a day, and we still had no more than eight to nine weeks to analyze and re-write our airline's schedule, which we still did five times a year by hand.  Clearly, the size of the job we had to do in the time allotted had grown enormously, the complexity of the job had increased, and our system had grown exponentially, but given our process, we had no more time nor available manpower to apply.  It became clear to the Company that we had to find a way to bring computer technology into the mix to help us work quicker and work better.  We had to be able to look at more scenarios and produce a more effective schedule that was more convenient for our Customers QUICK! Unfortunately, in talking to experts in optimization theory across the industry (believe it or not, airline schedule optimization is quite the science!), we found that our network had become too dense and large to solve, given the limitations of the science and technology at the time.  The roadblock turned out to be our basic business model!  In a previous blog post, I explained the difference between our point-to-point network and a hub-and-spoke airline network (click here to read that post).  For a variety of reasons (which I won't bore you with!) hub-and-spoke networks are relatively easy to schedule.  Point-to-point networks are very hard to schedule because there are vastly more options in departure times, ways to "hook together" flights, and many other factors.  One optimization scientist said that, based on the size of our network at the time, there were 1023 (that's the number ten followed by 23 zeros!) of different possible combinations of our set of flights, departure times and "hook-ups" that could comprise a valid, flyable Southwest Airlines schedule.  Looking back at my years of writing ever-increasingly more complex schedules, I suddenly realized why my hair had gone gray.  To think, I had been blaming the "snow on my roof" on my son!   As we continued to research optimization shops, one of the Southwest Airlines Employees on the Schedule Optimization Team came back to the office after Christmas break and showed us an optimized schedule output that was unlike anything we'd seen before.  It still needed work, but it had conquered the major hurdle, treating every single flight's departure time and hook-up in the network as a variable.  We were amazed and VERY excited.  Which of the optimization companies had produced this, we asked?   None of them, he replied.  He had cracked the problem on his own and produced the solution himself, over Christmas break, on his home PC, metaphorically, in his garage.  He had done what was actually thought to be mathematically and technologically impossible at the time.  THE ''GARAGE-O-MIZER" WAS BORN!   The rest of the story is the stuff of Southwest legend.  We continued to refine the process and calibrate the over 2,300 parameters in the optimization process for what seemed like forever, but we began flying our first, fully optimized schedule in October 2004 (which we dubbed the "Optober" schedule).  The magnitude of change we were able to incorporate into the schedule was staggering.    We continued to refine the optimization process, and by February 2006, we began flying our second reoptimized schedule, which, ultimately, generated millions of dollars in added revenue for the Company and our Shareholders.   Going forward, we plan to take maximum advantage of weather changes from winter, into summer, and back into winter.  Flights typically take less time in the warm weather months than they do in cold months, and optimization technology will allow us to take advantage of shorter flying times by putting even more flights into our schedule without investing in more aircraft.   We hope you like our new schedules, and we hope that you appreciate the time and effort we've spent in making our network even more convenient for you.  Now get out there; fly somewhere on Southwest;and exercise your freedom to move about our Country!
24 Comments
John_Jamotta
Not applicable
Bill, Outstanding post. Let me be the first to say congratulations. John
BLD
Not applicable
Bill- great story! I have noticed how much more flexible the flight schedules have become since my days with Southwest. Working in corporate travel, I see the ebb and flow in flight demand based on the day of the week and your system will help you deploy aircraft when and where needed.
Jeremiah_Jackso
Not applicable
OK, so next time I have to do an aircraft swap, I should blame it on computers, right?? jk!! At least then I get time for lunch!!!!! It's amazing and mind boggling just to think about such a large operation working together and...well...work!!
Drew1
Not applicable
Fascinating post! Can you point to an example flight that exists or a market that is better served as a result of this optimization? I am curious to see the fruits of this increased efficiency.
Dave511
Not applicable
So did that employee on the Schedule Optimization Team receive a nice big bonus that year, or at least an Employee of the Quarter award? 🙂
Bob_Hurst__4302
Not applicable
Another great post Bill! It is truly amazing what CAN be done when people simply ignore those who are sure it CANNOT be done. Someone should tell the story of our SWIFT system too ... another key to our success.
nsx1
New Arrival
The October 2004 changes were quite noticeable in the West Coast markets. Flights that had been uniformly spaced throughout the day became much better clustered around peak hours. I imagine that this was accomplished by linking these flights to long-haul east-west flights rather than simply bouncing aircraft up and down the West Coast. Because Southwest's "pay to fly earlier" standby policy allows it to charge more for peak hour flights, this West Coast move alone must have generated a significant revenue boost. Congratulations on pulling it off! Are your people going to publish any technical papers on your scheduling algorithms?
James5
Not applicable
Bill - great post! Keep up the great work! James Malone MDW FA
joan_miller
Not applicable
I don't have a web site but I am a "flying Grandma". Go to Phoenix to see the kids and love SWA. The only comment I have is, " What happened to the sense of humor the cabin attendents had? I've had some non-pluss type folks on my flights. Are you considering robots for cabin attendents and this is the training? Bring back the humans with humor and caring, they make the flight more fun.
jballard
Not applicable
Wonderful story, Bill. Another great example at SWA of individuals going over and above what is thought to be their limits to get the job done. The Warrior Spirit lives! How lucky are we to have such employees working for us? Thanks to you all for doing a trememdous job! Luv ya/mean it!
Bill
Employee
Employee
Hi, everyone....here are some answers to some of the questions you've posed in your blog comments. Yanqui: Excellent question. We could easily tell where we needed to improve the schedule, but given the time allotted, we simply didn't have the time to "rip things up" and put them back together again. Being able to generate and score millions of possible solutions was what the optimizer did best!!! Here are a few examples: Before the October 2004 optimization run, our single daily nonstop between Austin and Orlando left Austin at 7:55 p.m. and arrived at 11:15 p.m.--and for a leisure-oriented flight, most folks typically want to leave in time to arrive at their destination just around check-in time. Post-optimization, the flight shifted to depart Austin at 2:10 p.m. and arrived Orlando at 5:05 p.m. Much better from a demand perspective. Another example, in a higher-frequency market, was Raleigh/Durham to Baltimore. Pre-optimization, our departures were at 7:30 a.m., 11:00 a.m., 11:30 a.m., 2:55 p.m., 6:00 p.m., and 8:00 p.m. Note the BIG compression with flights at 11:00 and 11:30, then a big gaps in mid-morning and mid-afternoon. Post-optimzation departure times in the market moved to 6:55 a.m., 8:45 a.m., 11:25 a.m., 2:30 p.m., 5:40 p.m., and 8:40 p.m. Clearly it's much more evently-spaced with fewer gaps and less compression. Opitmization saves the day again! Thanks for the question! Next: Dave, yes, the amazingly creative Technology Employee did receive an award. He was one of the recipients of the Southwest Airlines President's Award in 2002. See, we try to take care of our own! ;) Next: Bob, you're right. SWIFT....our internet site...and my personal favorite, our new schedule editing tool, SPN which was developed entirely in house and is not just incredibly functional--it's eye candy as well. You guys in Technology ROCK!!!! And finally: nsx, no, the algorithm developed for our schedule optimization process is a very tightly-guarded secret. Even at some of the optimization conferences, we're all ears but have zipped lips about how we "cracked" the problem. We LUV for our competitors to be as in the dark about how we succeed as possible! Thanks everyone for reading "Nuts about Southwest" and for the excellent comments and questions. Please keep them up! Bill
Chris3
Not applicable
Bill, Do you have a date for when the Christmas flight schedules will be up? Chris
Jim_Porett
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Hi Bill, Great article! As the college roommate of the employee you wrote about, I can attest that he's a brilliant guy! 😉 Until he started working at SWA, I never realized how amazingly complex it is to setup flight schedules. Makes me appreciate even more what a great job you all do! Regards, Jim
nsx1
New Arrival
I've long been curious as to why schedule extensions typically happen at 10 AM Central Time on Thursdays. Is there a meeting early Thursday when your management blesses your work and gives the OK to throw the switch? People wanting advance notification of schedule extensions should install Ding, which will notify them immediately of the extension. My personal guess for the next extension is 10 AM Central Time on August 17, for travel through January 14 or so.
Gary20
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Hi there! As a scheduler with another carrier, I got a huge kick out of your comments! This, once again, just goes to prove that it's the PEOPLE who make the difference
A_Fraser
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Sorry to rain on your parade, but IÃ
joe-mdw-plane-d
Not applicable
A Fraser, There was only one n/s from Vegas to DTW. It was on a Saturday for about three monthes. Not sure where your info on the other cities being n/s to DTW comes from. Are you perhaps refering to several years ago?
Roger2
Not applicable
Why have the morning flights from BWI to BOI been dropped? We can not even make a connection and get to BOI in the early afternoon. If you do not arrive until six to eight p.m and then have to drive another three or four hours it makes for a really long day or an overnight stay in Boise. I hope that an earlier flight will be added back to the schedule. Thanks
Scott5
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How does the optimizer factor in our wish list (example MSY-BHM) or other increased existing service? How does it affect the possible opening of Love to more cities directly (if the agreement passes)?
Gail3
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The story was very good and full of info. We have a complaint though. We are Rapid Reward members, and it just seems to us our flights have been getting off later and later, always some delay from the departing airport. What's up with it? We love SouthWest! We just don't like to be late for anything. thanks for the blog! Gail from Mass. flys out of Manchester, NH
blusk
Not applicable
Hi Gail, Thanks for your comment and your patronage! As you can tell from Bill's post, we have some pretty amazing folks in our Schedule Planning Department. I'm also sorry to hear that you have encountered some flight delays from Manchester. As you are probably aware, the Northeast has been experiencing some strong weather this summer--we could sure use that rain down here in Texas. Please understand that, without specific flight details, I can't speak to your specific flights. However, this year, Air Traffic Control is trying a new system called AFP (Airspace Flow Program) that is designed to keep the entire traffic in the Northeast flowing smoothly. Even though weather may not be affecting your specific airport, it may be affecting the general area. Without AFP, some flights may have operated on schedule, but many others may have had to divert to alternate airports. My fellow blogger, Fred Taylor, wrote an earlier post about AFP, and you can access it here. Fred does a much better job of explaining it than I can. Brian
Herb
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Bill" Why is it that SWA does not serve Savannah,Ga/and or Charleston,sc
djs1
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Any idea when summer 2007 flights will open?
Steven_Holty
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Bill, your garage-o-mixer turned into true schedule optimizer this year is fascinating. I understand you want to keep it proprietary, as would I. We met with Northwest and they too put out a marketing schedule. I'm not sure how they do that either. What I'm very curious about is how Southwest applies tail numbers to the marketing plan. And how you get maintenance activies completed. Who or where might I talk to about that? Steven