About 1 in 3 DL 3999 flights from Santa Ana arrived 15+ minutes late, diverted or cancelled over the past year (31%); 0.7% were cancelled. The typical flight landed 1 minutes late.
DL 3999: SNA → SEA
Scheduled to leave Santa Ana at 5:25 p.m. local time, operated by SkyWest as OO 3999. Over the past year it arrived on time 69% of the time (137 flights), worse than other DL flights on the route at that hour (74%). Last seen in the data Aug 31, 2026.
Month by month
By day of week
| Day | Flights | On time |
|---|---|---|
| Monday | 21 | 62% |
| Tuesday | 20 | 75% |
| Wednesday | 20 | 75% |
| Thursday | 20 | 70% |
| Friday | 20 | 65% |
| Saturday | 16 | — |
| Sunday | 20 | 60% |
Why it was late
All flights SNA → SEA · Connecting off DL 3999? Check the risk
DL 3999: SEA → SNA
Scheduled to leave Seattle at 1:40 p.m. local time, operated by SkyWest as OO 3999. Over the past year it arrived on time 69% of the time (137 flights), in line with other DL flights on the route at that hour (72%). Last seen in the data Aug 31, 2026.
Month by month
By day of week
| Day | Flights | On time |
|---|---|---|
| Monday | 21 | 52% |
| Tuesday | 20 | 80% |
| Wednesday | 20 | 85% |
| Thursday | 20 | 60% |
| Friday | 20 | 75% |
| Saturday | 16 | — |
| Sunday | 20 | 65% |
Why it was late
All flights SEA → SNA · Connecting off DL 3999? Check the risk
Questions
How often is DL 3999 from SNA to SEA late?
Delta Air Lines 3999 from Santa Ana, CA to Seattle, WA arrived 15 or more minutes late, was diverted or was cancelled on 31% of 137 scheduled flights between September 2025 and August 2026. 0.7% were cancelled.
How often is DL 3999 from SEA to SNA late?
Delta Air Lines 3999 from Seattle, WA to Santa Ana, CA arrived 15 or more minutes late, was diverted or was cancelled on 31% of 137 scheduled flights between September 2025 and August 2026. 0.7% were cancelled.
Flight numbers change. Figures cover flights with this airline, number and route only. "Likely range" is the 95% interval for the true on-time rate given the number of flights. This is history, not live status: check Delta Air Lines for today's flight. Method.