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Flight Reliability

DL 3909 · Delta Air Lines

Detroit → AZO (DTW–AZO)95% of its flights flew this route. The rest (DTW–MKE) are included in these numbers.

61
A Little Dicey
WanderNerd Reliability Score
74%
Arrive within 15 minutes
33 min
Average arrival delay
2.1%
Cancelled
7 min early
Median arrival delay

Based on 336 historical flights. Data through May 2026.

What the data says

The late departure is the smart one here.

DL 3909 departing between 6–9 PM arrived on time 82% of the time, versus 73% between 9 PM–12 AM.

Sunday scaries are real for this one.

DL 3909 arrived on time 95% of the time on Saturdays and just 67% on Sundays. That gap is worth planning around.

A bit behind the Delta Air Lines network.

DL 3909 arrived on time 74% of the time, versus 81% across the Delta Air Lines network.

Trending in the right direction.

DL 3909 arrived on time 72% of the time over the last three months in the data, compared with 58% in the three months before that.

The breakdown

On-time by weekday
  • Mon77%(51 flights)
  • Tue70%(43 flights)
  • Wed70%(43 flights)
  • Thu71%(49 flights)
  • Fri73%(48 flights)
  • Sat95%(42 flights)
  • Sun67%(52 flights)
On-time by departure window
  • 3–6 PM—(2 flights)
  • 6–9 PM82%(45 flights)
  • 9 PM–12 AM73%(281 flights)
On-time trend by month
71%
May

Jun 62% → May 71% on time

On-time arrival percentage by month
MonthOn-time percentageFlights
June 202562%29
July 202567%30
August 202584%31
September 2025100%30
October 202594%31
November 202577%26
December 202568%31
January 202644%18
February 202663%16
March 202662%26
April 202683%29
May 202671%31
Departures on time
75%
Diverted
0.3%
Flights flown
328
Months covered
12

Same route, other flights

Keep nerding

Based on 336 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.