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Flight Reliability

DL 3991 · Delta Air Lines

This number covered several routes in this period.

One number, several routes.

Airlines reuse flight numbers, and DL 3991 moved between routes during this period. Numbers below combine all of them, so treat them as background, not a verdict. For a cleaner answer, check the route you are actually flying.

Combined across all its routes

77%
Arrive within 15 minutes
5 min
Average arrival delay
0.6%
Cancelled
4 min early
Median arrival delay

Based on 617 historical flights. Data through May 2026.

The breakdown

On-time by weekday
  • Mon82%(92 flights)
  • Tue81%(90 flights)
  • Wed70%(90 flights)
  • Thu74%(89 flights)
  • Fri69%(83 flights)
  • Sat93%(76 flights)
  • Sun74%(93 flights)
On-time by departure window
  • 6–9 AM89%(47 flights)
  • 3–6 PM77%(283 flights)
  • 6–9 PM76%(283 flights)
On-time trend by month
60%
May

Jun 89% → May 60% on time

On-time arrival percentage by month
MonthOn-time percentageFlights
June 202589%53
July 202593%58
August 202588%58
September 202572%46
October 202569%54
November 202568%50
December 202580%50
January 202690%30
February 202685%39
March 202674%53
April 202670%60
May 202660%62
Departures on time
83%
Diverted
0%
Flights flown
613
Months covered
12

Keep nerding

Based on 617 historical flights, because apparently we checked. Historical flight data: U.S. Bureau of Transportation Statistics, June 2025 – May 2026. Data through May 2026. How we calculate this.