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Flight Reliability

DL 321 · Delta Air Lines

Boston → Los Angeles (BOS–LAX)97% of its flights flew this route. The rest (DEN–ATL, ATL–CAE) are included in these numbers.

59
A Little Dicey
WanderNerd Reliability Score
69%
Arrive within 15 minutes
24 min
Average arrival delay
2.2%
Cancelled
2 min
Median arrival delay

Based on 278 historical flights. Data through May 2026.

What the data says

The 3–6 PM departure wins.

DL 321 departing between 3–6 PM arrived on time 75% of the time, versus 62% between 6–9 PM.

Sunday scaries are real for this one.

DL 321 arrived on time 78% of the time on Saturdays and just 59% on Sundays. That gap is worth planning around.

Lagging the BOS–LAX route.

DL 321 arrived on time 69% of the time, versus 77% across the BOS–LAX route.

Lagging the Delta Air Lines network.

DL 321 arrived on time 69% of the time, versus 81% across the Delta Air Lines network.

The breakdown

On-time by weekday
  • Mon65%(43 flights)
  • Tue73%(33 flights)
  • Wed71%(41 flights)
  • Thu66%(41 flights)
  • Fri74%(42 flights)
  • Sat78%(27 flights)
  • Sun59%(44 flights)
On-time by departure window
  • 6–9 AM—(1 flights)
  • 12–3 PM—(4 flights)
  • 3–6 PM75%(128 flights)
  • 6–9 PM62%(138 flights)
On-time trend by month
67%
May

Jun 64% → May 67% on time

On-time arrival percentage by month
MonthOn-time percentageFlights
June 202564%25
July 202565%20
August 202582%17
September 202547%17
October 202546%22
November 202575%20
January 202689%28
February 202663%27
March 202680%30
April 202670%30
May 202667%27
Departures on time
71%
Diverted
0.4%
Flights flown
271
Months covered
12

Same route, other flights

Keep nerding

Based on 278 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.