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Flight Reliability

DL 1221 · Delta Air Lines

Milwaukee → Atlanta (MKE–ATL)

91
Nerd Approved
WanderNerd Reliability Score
91%
Arrive within 15 minutes
1 min early
Average arrival delay
1.6%
Cancelled
16 min early
Median arrival delay

Based on 365 historical flights. Data through May 2026.

What the data says

Sunday scaries are real for this one.

DL 1221 arrived on time 94% of the time on Thursdays. On Sundays: 87%.

Better than the Delta Air Lines network average.

DL 1221 arrived on time 91% of the time, versus 81% across the Delta Air Lines network.

Trending in the right direction.

DL 1221 arrived on time 90% of the time over the last three months in the data, compared with 83% in the three months before that.

The breakdown

On-time by weekday
  • Mon92%(49 flights)
  • Tue88%(51 flights)
  • Wed88%(51 flights)
  • Thu94%(52 flights)
  • Fri94%(52 flights)
  • Sat92%(51 flights)
  • Sun87%(52 flights)
On-time by departure window
  • 3–6 AM91%(356 flights)
  • 6–9 AM—(2 flights)
On-time trend by month
87%
May

Jun 100% → May 87% on time

On-time arrival percentage by month
MonthOn-time percentageFlights
June 2025100%29
July 202590%30
August 202597%31
September 2025100%30
October 202594%31
November 202593%27
December 202577%31
January 202677%31
February 202693%28
March 202690%30
April 202693%29
May 202687%31
Departures on time
94%
Diverted
0.3%
Flights flown
358
Months covered
12

Same route, other flights

Keep nerding

Based on 365 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.