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Flight Reliability

DL 3979 · Delta Air Lines

San Jose → Los Angeles (SJC–LAX)89% of its flights flew this route. The rest (GRR–DTW) are included in these numbers.

99
Nerd Approved
WanderNerd Reliability Score
95%
Arrive within 15 minutes
7 min early
Average arrival delay
0.6%
Cancelled
16 min early
Median arrival delay

Based on 336 historical flights. Data through May 2026.

What the data says

Skip Thursday if you can.

DL 3979 arrived on time 100% of the time on Sundays. On Thursdays: 91%.

A bit ahead of the SJC–LAX route.

DL 3979 arrived on time 95% of the time, versus 88% across the SJC–LAX route.

Better than the Delta Air Lines network average.

DL 3979 arrived on time 95% of the time, versus 81% across the Delta Air Lines network.

Recent months have been rougher.

DL 3979 arrived on time 87% of the time over the last three months in the data, compared with 95% in the three months before that.

The breakdown

On-time by weekday
  • Mon94%(48 flights)
  • Tue92%(49 flights)
  • Wed96%(46 flights)
  • Thu91%(46 flights)
  • Fri96%(48 flights)
  • Sat94%(48 flights)
  • Sun100%(48 flights)
On-time trend by month
90%
Apr

Jun 93% → Apr 90% on time

On-time arrival percentage by month
MonthOn-time percentageFlights
June 202593%30
July 2025100%31
August 2025100%31
September 2025100%30
October 2025100%30
November 202590%30
December 202596%27
January 2026100%30
February 2026100%28
March 202670%30
April 202690%30
Departures on time
95%
Diverted
0.3%
Flights flown
333
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.