Flight Reliability
DL 4439 · Delta Air Lines
Sacramento → Seattle (SMF–SEA)
94
Nerd Approved
WanderNerd Reliability Score
- 93%
- Arrive within 15 minutes
- 3 min early
- Average arrival delay
- 1.6%
- Cancelled
- 13 min early
- Median arrival delay
Based on 122 historical flights. Data through May 2026.
What the data says
Friday is doing you no favors.
DL 4439 arrived on time 100% of the time on Tuesdays and just 81% on Fridays. That gap is worth planning around.
Better than the SMF–SEA route average.
DL 4439 arrived on time 93% of the time, versus 83% across the SMF–SEA route.
Better than the Delta Air Lines network average.
DL 4439 arrived on time 93% of the time, versus 81% across the Delta Air Lines network.
The breakdown
- Mon94%(17 flights)
- Tue100%(18 flights)
- Wed100%(18 flights)
- Thu100%(17 flights)
- Fri81%(16 flights)
- Sat88%(17 flights)
- Sun82%(17 flights)
93%
Apr
Jan 89% → Apr 93% on time
| Month | On-time percentage | Flights |
|---|---|---|
| January 2026 | 89% | 26 |
| February 2026 | 96% | 28 |
| March 2026 | 90% | 30 |
| April 2026 | 93% | 30 |
- Departures on time
- 93%
- Diverted
- 0%
- Flights flown
- 120
- Months covered
- 5
Same route, other flights
Keep nerding
Based on 122 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.