Skip to content
WanderNerd
Check a flight

Flight Reliability

DL 640 · Delta Air Lines

San Francisco → Atlanta (SFO–ATL)

97
Nerd Approved
WanderNerd Reliability Score
91%
Arrive within 15 minutes
3 min early
Average arrival delay
0.5%
Cancelled
11 min early
Median arrival delay

Based on 364 historical flights. Data through May 2026.

What the data says

Better than the SFO–ATL route average.

DL 640 arrived on time 91% of the time, versus 82% across the SFO–ATL route.

Better than the Delta Air Lines network average.

DL 640 arrived on time 91% of the time, versus 81% across the Delta Air Lines network.

Slipping a little lately.

DL 640 arrived on time 89% of the time over the last three months in the data, compared with 94% in the three months before that.

The breakdown

On-time by weekday
  • Mon90%(51 flights)
  • Tue90%(52 flights)
  • Wed92%(52 flights)
  • Thu92%(52 flights)
  • Fri90%(51 flights)
  • Sat90%(51 flights)
  • Sun91%(53 flights)
On-time trend by month
84%
May

Jun 87% → May 84% on time

On-time arrival percentage by month
MonthOn-time percentageFlights
June 202587%30
July 202584%31
August 202581%31
September 202597%30
October 202593%30
November 2025100%29
December 202594%31
January 202694%31
February 202696%28
March 202697%30
April 202687%30
May 202684%31
Departures on time
91%
Diverted
0%
Flights flown
362
Months covered
12

Same route, other flights

Keep nerding

Based on 364 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.