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Flight Reliability

DL 821 · Delta Air Lines

Atlanta → Boston (ATL–BOS)

64
A Little Dicey
WanderNerd Reliability Score
67%
Arrive within 15 minutes
18 min
Average arrival delay
1.6%
Cancelled
3 min
Median arrival delay

Based on 321 historical flights. Data through May 2026.

What the data says

6–9 PM has a slight edge.

Departures between 6–9 PM arrived on time 69% of the time, against 64% between 3–6 PM.

Sunday scaries are real for this one.

DL 821 arrived on time 73% of the time on Tuesdays and just 57% on Sundays. That gap is worth planning around.

Lagging the ATL–BOS route.

DL 821 arrived on time 67% of the time, versus 74% across the ATL–BOS route.

Lagging the Delta Air Lines network.

DL 821 arrived on time 67% of the time, versus 81% across the Delta Air Lines network.

The breakdown

On-time by weekday
  • Mon66%(47 flights)
  • Tue73%(40 flights)
  • Wed70%(40 flights)
  • Thu62%(47 flights)
  • Fri69%(49 flights)
  • Sat72%(46 flights)
  • Sun57%(47 flights)
On-time by departure window
  • 3–6 PM64%(142 flights)
  • 6–9 PM69%(174 flights)
On-time trend by month
65%
May

Jun 50% → May 65% on time

On-time arrival percentage by month
MonthOn-time percentageFlights
June 202550%26
July 202528%18
August 202569%16
September 202565%20
October 202560%30
November 202575%28
December 202571%31
January 202686%29
February 202673%26
March 202671%31
April 202673%30
May 202665%31
Departures on time
65%
Diverted
0%
Flights flown
316
Months covered
12

Same route, other flights

Keep nerding

Based on 321 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.