Harvard Study: Airlines Pad Schedules as 3‑Hour Delays Quadruple Since 1990

A Harvard study released in August 2025 finds that long U.S. flight delays have surged while airlines quietly add extra time to published schedules. Three-hour delays are now four times more common than in 1990, and carriers have turned to “schedule padding”—adding an average of 20 minutes to block times—to keep official on-time numbers steady even as real-world delays grow. Harvard researcher Maxwell Tabarrok analyzed decades of federal data and ties the trend to worsening congestion, aging infrastructure, and staffing shortages, especially among air traffic controllers. The result: longer scheduled trips that often arrive “on time” by definition, even when passengers feel the slowdown.

Key findings from the Harvard review

Tabarrok’s review of 30 years of Bureau of Transportation Statistics data shows a 400% increase in 3+ hour delays since 1987. His analysis, widely cited in August 2025, highlights a shift that began around 2000, when scheduled and actual times started to diverge.

• From 1987 to 2000, scheduled and actual flight times stayed close.
• After 2000, the gap grew as airlines systematically stretched schedules—a deliberate response, he argues, to deteriorating conditions while aiming to protect on-time performance metrics.

Airlines are now padding schedules across the board, with the average buffer rising to 10–15% of total flight time in 2025. Some carriers add more than others:

• Southwest Airlines: 13.9%
• Alaska Airlines: 11.3%
• United Airlines: 10.2%
• Frontier Airlines: 6.8%
• Allegiant Air: 6.4%
• Hawaiian Airlines: 4.7%

The Department of Transportation defines “on time” as arriving within 15 minutes of the scheduled time. Because schedules have been lengthened, airlines can claim punctuality even when flights take longer than they did years ago.

For official on-time and delay data, the Bureau of Transportation Statistics provides public reports at https://www.bts.gov/topics/airlines-and-airports/airline-on-time-performance-data.

Important: As of 2024, more than 20% of U.S. flights still faced a delay despite padding.

Reactions from industry and experts

Tabarrok summarizes the timeline bluntly:
“For 15 years, from 1987 to 2000, the actual and scheduled times stayed very close together. Then, starting right around 2000, they started diverging—a pretty clear sign airlines made a decision to start padding their schedules to avoid shorter delays.”

Industry voices offer differing views:

• Max Barrus, vice president at Breeze Airways, defends padding: “If you didn’t do that, nobody would ever be on time.”
• Aviation professor Jeff Price compares padding to leaving early for a car trip to account for traffic and surprises along the way.

Regulators have not moved to restrict schedule padding. As of August 14, 2025, no major regulatory reforms address the practice or the core causes of worsening delays. FAA staffing shortfalls and aging infrastructure remain key bottlenecks, and airport expansion still faces bureaucratic and environmental hurdles that slow capacity upgrades.

Industry strategies and hidden costs

Schedule padding gives airlines several operational advantages:

• Protects published reliability
• Limits compensation claims tied to late arrivals
• Smooths daily operations by reducing knock-on delays

But padding also has clear downsides:

• Strains efficiency: aircraft and crews spend more time blocked per trip
• Lowers asset utilization and raises labor and fuel costs
• Shifts real time costs to passengers in lost personal and productive time

Estimated economic impact: the added minutes built into schedules come with an annual cost of about $6 billion in lost time, based on average wage data cited in the Harvard study.

How airlines implement padding (simplified)

1. Review route-by-route history (congestion, weather, airport quirks).
2. Add extra minutes to block time to hit the DOT’s 15-minute on-time target.
3. Report performance against the padded schedule rather than against historical actuals.
4. Present improved punctuality even as real travel times lengthen and three-hour delays climb.

Consumer advocates call the practice misleading because it hides systemic problems. Airline officials say it’s a necessary hedge. Industry analysts warn that unless root causes—controller staffing, infrastructure, and airspace congestion—are fixed, padding will keep rising, dragging down the overall efficiency of U.S. air travel.

What this means for travelers

Passengers now face longer planned journeys and more “on-time” arrivals that still feel late. This affects:

• Families traveling to events
• Business travelers with tight schedules
• Travelers coordinating international connections

Practical implications and planning tips:

• Expect more buffer time built into published schedules.
• Allow extra time for connections and for ground plans after landing.
• Avoid assuming “on-time” equals a shorter trip—paper punctuality may mask longer door-to-door travel.

Analysis by VisaVerge.com underlines a central reality: published schedules no longer reflect past flight durations, and buffers are now standard practice rather than rare exceptions.

Long-term outlook and policy context

Historically, the split between scheduled and actual times was modest from the late 1980s through 2000. The divergence accelerated in the 2010s and into the 2020s. The COVID-19 rebound pushed heavy demand into a system still hampered by aging facilities and staffing issues. By 2025, schedule padding is routine, and long delays sit at record levels for the modern era.

Proposed fixes—such as more FAA funding, faster airport projects, and new traffic management tools—are frequently cited but have not yet produced system-wide change. With no quick policy breakthroughs, padding acts as a short-term pressure valve: it improves the scorecard but does not shorten trips for passengers.

Key takeaways:
– Three-hour delays have multiplied.
– Average padding sits at 20 minutes per flight.
– More than a fifth of flights in 2024 still ran late.
– The DOT’s 15-minute on-time rule gives airlines room to stretch schedules.
– The nation incurs roughly $6 billion a year in lost time while waiting for deeper fixes.

The Harvard study’s message is clear: the numbers have moved in the wrong direction, and the calendar has not delivered a policy reset. Without addressing underlying capacity and staffing issues, schedule padding will likely remain part of airline planning—increasing apparent punctuality but not passengers’ actual travel speed.