Keji Wei Th’19 spends every working day thinking about disasters. Unexpected catastrophes such as typhoons and earthquakes wreak havoc on lives, including plans to visit loved ones, sightsee in a foreign land, or just try to get back home. It’s Wei’s job to plan around and overcome these obstacles to get people to where they need to go.

Wei works as a senior operations research analyst at Sabre Corp., a leading technology solutions provider to the travel industry, and is stationed at the company’s global headquarters in Southlake, Texas, outside of Dallas. At Sabre, Wei acts as an airline consultant by using available data and mathematical models to provide real-time solutions to customers whose travel has been disrupted for any number of reasons.

“I design disrupted passengers’ itineraries for airlines all over the world,” says Wei. “For each airline, my job is to design a model and its corresponding solution approach for the purposes of assigning the optimal flight to each disrupted passenger.”

So, the next time your flight is successfully rebooked after a volcano eruption or tornado spoils your initial ride, you might want to thank Wei.

Wei is responsible for generating parameters for every imaginable travel scenario. He has to consider the numbers of available aircrafts and disrupted passengers when trying to find a solution that works for everyone—passengers and airlines—and then he analyzes and answers questions that may arise.

Wei also utilizes operations research to minimize the ripple effect of one delay on subsequent flights, a phenomenon known as delay propagation, through smart-planning of crew itineraries. Wei says his biggest daily motivation is to help airlines save millions of dollars—costs then passed on to consumers—by optimizing their own itineraries using mathematical models.

“My hope is to improve airline efficiency and make travel smart by using my mathematical knowledge,” he says.

The prestigious Mathematical Contest in Modeling initially sparked Wei’s interest in the airline industry. He first competed in the international challenge when he was 19 years old, and just a few years later he was named a meritorious winner of the multi-day competition.

“I was attracted to the airline industry because I wanted to design mathematical models and solution approaches to solve practical problems in the real world,” says Wei.

A year later, in 2011, Wei received his BE from Xi’an Jiaotong University in his native country of China, along with its Best Undergraduate Thesis Award. After spending some time as a project officer at Nanyang Technological University in Singapore, where he focused on energy-efficient, rail-guided vehicle routing, he landed at Thayer in the fall of 2014.

Wei became the first Dartmouth PhD advisee of Professor Vikrant Vaze. In fact, Wei applied to Thayer before Vaze was officially a member of the full-time faculty.

“My first read of Vaze was that he is very serious,” says Wei. “After that, we had a good time. He will always be a friend of mine.”

“We connected over Skype and discussed each other’s research interests,” says Vaze about his initial connections with Wei. “From the beginning, Keji came across as someone who is truly passionate about research and enthusiastic and open to trying out and evaluating new ideas.”

Once they were both at Thayer, Wei worked with Vaze on five major transportation-related research efforts:

• Quantifying and analyzing the ripple effect a delayed flight has on subsequent flights due to the scheduling of crew itineraries;
• Optimizing airline timetables and fleet assignments by incorporating passenger choice, such as preferred departure times;
• Conducting simulation analysis comparing point-of-care testing and central laboratory testing;
• Solving large-scale crew scheduling problems; and
• Optimizing transit schedules by considering traffic congestion, passenger choice, and ride-hailing services such as Uber and Lyft.

“Over a five-year period, I feel as if Keji and I had a seemingly infinite number of meetings, brainstorming sessions, agreements, disagreements, bottlenecks, discoveries, failures, and triumphs, the pace of which seemed relentless,” says Vaze. “I was often impressed by Keji’s hard work and his attention to detail, especially when it came to solving really hard, large-scale optimization problems.”

Their partnership took flight, earning them accolades amid a flurry of peer-reviewed academic papers that were jointly written. The pair often worked with Alexandre Jacquillat, an assistant professor of operations research and statistics at the MIT Sloan School of Management; Jacquillat later became one of Wei’s thesis co-advisors.

“It was fun and challenging,” says Wei. “I have a lot of really sweet memories of being supervised by them.”

In 2019, while Wei was wrapping up his PhD research at Thayer, he received the Anna Valicek Award at the Airline Group of the International Federation of Operational Research Societies (AGIFORS) symposium. Wei earned the honor with his paper, “Airline Timetable Development and Fleet Assignment Incorporating Passenger Choice,” which he coauthored with Vaze and Jacquillat.

“The most amazing thing is that this was Keji’s second Anna Valicek medal,” says Vaze. “He won a runner-up medal two years prior for a different paper we co-authored.”

At the same time that Wei received his medal, Vaze and Jacquillat were awarded the Transportation Science and Logistics Outstanding Paper Award in Air Transportation at the Institute for Operations Research and the Management Sciences annual meeting. Vaze’s work has also been honored with best paper awards from AGIFORS in 2010, 2017, and 2019 and from the Federal Aviation Administration (FAA) and Eurocontrol in 2011 and 2017. He is the recipient of a number of academic and industry honors, including the National Science Foundation’s Faculty Early Career Development Program Award and awards from the U.S. Department of Defense, FAA, National Institutes of Health, and World Wildlife Fund.

Most recently, Wei was the first author on a paper with Vaze and Jacquillat that presented an original approach that could benefit the airline industry with profitable improvements and passengers with preferable travel timetables.

“Beyond ticket prices, perhaps the biggest thing that air passengers care about is the convenience of flight schedule. Yet, due to the associated computational complexities, nobody has ever before really tried to completely redesign an airline’s flight schedule from scratch to take passenger preference into account,” says Vaze.

In recognition of his achievements, Vaze was named the Stata Family Career Development Assistant Professor of Engineering, a title bestowed upon him this spring by the Dartmouth Board of Trustees. The endowment supports a member of the Thayer School faculty by creating a career development fellowship to leverage growth in teaching, research, or scholarship.

“I felt really humbled to receive that honor, especially since it is named after a family of such inspirational technology innovators and entrepreneurs,” says Vaze.

Meanwhile, after earning his PhD in operations research from Thayer late last year, Wei has settled into life after academia—though he hasn’t forgotten it. Wei says he hopes to fill the gap between academia and the transportation industry by implementing cutting-edge research and relying on his engineering education.

“Thayer is definitely a magical place for you to explore your research idea, and the school will help build you up not only as an independent researcher, but also as a better person,” says Wei. “The most impressive part of Thayer is that students have unlimited chances to interact with other students of totally different backgrounds who are all so talented. I learned how to communicate and share with others, and that type of interactive environment is rarely achieved in any other school in the world.”

When asked what advice he would give to current and prospective Thayer students, Wei says: “Jump out of your comfort zone and be independent, confident, and persistent.”

Just don’t fly by the seat of your pants.

—Julie Bonette is a contributing editor to Dartmouth Engineer

Flying in the Era of COVID-19

These transportation experts share thoughts on how the pandemic may affect the airline industry in the long term.

“One of the hardest-hit industries has been the travel industry and the airlines, in particular. Once this crisis is over, there might be an opportunity to press a complete reset button, for travelers to rethink behavior, and for the industry to reconfigure its service offerings—ideally for the better and towards a greener, kinder, more equitable and more resilient planet.”

—Professor Vikrant Vaze

“The airlines have severely cut their operations as a response, but the crisis will end at some point. Passenger transportation systems are integral to our lives and an important pillar of the global economy, so I predict the airline industry will build back up even better than in was before.”

— Keji Wei Th’19