Five extra minutes of scheduled boarding time cut Delta's departure delays

Adding five minutes to the scheduled boarding period helped Delta Air Lines flights leave the gate sooner and more reliably, according to researchers at the University at Buffalo School of Management. Departures were about 1.5 minutes earlier on average, and the likelihood of leaving on time rose by around one-third. The study is forthcoming in Production and Operations Management.

Two policies, one day

On 2 June 2022, Delta made two changes at once. For domestic narrow-body aircraft, it lengthened the planned boarding time from 35 to 40 minutes. It did not lengthen the whole turnaround; the time came from other gate activities such as deplaning, cleaning, refuelling and baggage handling. On the same day, Delta became the first US airline to pay flight attendants for boarding, at half their usual hourly rate.

Because the two changes coincided, separating their effects was the central analytical task. The team, led by Chandrasekhar Manchiraju of Michigan State University with Ashutosh Bhave of the University of Arkansas and Milind Sohoni of Buffalo, exploited the fact that the policies did not apply equally. Narrow-body flights received both changes, whereas wide-body flights received only the pay change. The researchers also compared Delta with American Airlines and United Airlines, using federal on-time performance data for April to July 2022 that covered about 622,000 flights.

What the data showed

The extra boarding time was associated with the improvement in punctuality. The authors explain that boarding is the final step before a aircraft leaves the gate, so any overrun passes straight into the departure time. Slack placed earlier in the turnaround can be absorbed before it matters; slack at the end cannot be missed in the same way.

The benefit varied across the network:

• Gains grew through the day, from about 0.8 minutes for morning flights to about 2.4 minutes for night flights, consistent with delays accumulating as the day goes on.
• On the busiest 10% of routes, delays fell by about 2.1 minutes, against 1.5 minutes elsewhere.
• Longer flights also benefited more.

Pay had no detectable effect on delays

The comparison found no empirical evidence that paying attendants for boarding reduced departure delays. Sohoni suggests that crews already face strong incentives to depart on time, including point-based reliability policies and on-time bonuses, so extra pay adds little. The authors stress that the pay policy may still matter for morale, retention and fair compensation, outcomes the study did not measure.

Costs and implications

Sohoni cites federal estimates that delays cost airlines, passengers and the wider economy $33 billion a year. By his figures, Delta's boarding change saves roughly $11 million a month in operating costs and about $12.5 million a month in passenger time. Paying attendants for boarding costs about $5.4 million a month, so the two policies together still came out ahead financially.

For operations researchers, the study is a worked example of targeting buffer time at the stage of a process where it has the greatest effect, instead of padding schedules uniformly. The finding that gains were largest late in the day and on congested routes suggests that slack could be allocated by time of day and route rather than set as a single fleet-wide figure.

The evidence comes from observational comparisons across airlines and aircraft types over a four-month window in 2022, rather than from a controlled trial, and it centres on one carrier's policy. Further work could test whether the pattern holds at other airlines, in other seasons, and for other stages of the gate turnaround.

Source: Giving passengers a bit more time to board helps flights leave on time (Tech Xplore, 5 November 2026).

Image: AI-generated illustration.