Flight number record
DL 1551
Delta Air Lines · Los Angeles to Seattle
- Route
- LAX → SEA
- Departs
- 19:59
- Flights
- 301
- Period
- September 2025 to August 2026
Historical statistics for September 2025 to August 2026, not live status. For today’s DL 1551, check with Delta Air Lines.
DL 1551 lands a B+, level with the national rate of 77.3%. Roughly one flight in five arrives 15 minutes late or worse, and those flights are late by about an hour on average. That rests on 301 flights, with a median arrival 11 minutes early.
Key figures
On time
77.9%
Arrivals under 15 minutes late, of 298 completed flights
Avg delay
65 min
Across delayed arrivals only, not all flights
Cancelled
0.33%
National rate is 1.89%
1 hour+ late
6.4%
National rate is 8.3%
These figures cover 301 flights between September 2025 and August 2026. The median arrival is 11 minutes early, which is the part an average hides: most flights here are fine, and the on-time rate is decided by a tail of badly late ones. On-time means under 15 minutes late, the DOT's own threshold.
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Schedule
When DL 1551 flies
DL 1551 flies LAX to SEA without a single fixed slot. Its most common scheduled departure was 19:59, used on 43 of 301 flights, with 19:35 (32 flights) next.
- Departs 19:5943 flights14.3%
- Departs 19:3532 flights10.6%
Scale runs 0% to 100%.
Share of scheduled departures at each local time. Times used on fewer than one flight in ten are not listed.
A 19:59 departure sits in the 5pm–8pm window. Across every US flight scheduled in that window the on-time rate is 68.0%, and DL 1551 runs 10 points better at 77.9%. By that time of day most aircraft have flown several legs already, and whatever went wrong earlier is still in the schedule.
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Against the route
DL 1551 next to LAX to SEA
Every carrier on LAX to SEA combined arrived on time 85.0% of the time across 7,534 flights, so DL 1551 is 7 points behind it. Delta flew 2,228 flights on the same city pair under all its flight numbers, including this one, and those ran 85.2% on time. Across its whole network Delta Air Lines managed 81.1%, which this flight trails by 3 points.
| Compared with | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| DL 1551thin sample | 301 | 77.9% | 65 min | 0.33% | B+ |
| All Delta Air Lines on LAX–SEA | 2,228 | 85.2% | 71 min | 0.67% | A+ |
| All carriers on LAX–SEA | 7,534 | 85.0% | 62 min | 0.84% | A+ |
| Delta Air Lines, whole network | 1,039,517 | 81.1% | 71 min | 1.74% | B |
Across the year
DL 1551 quarter by quarter
DL 1551 did not run the same all year. Its best quarter was Jul–Sep 2025 at 100.0% on time and its weakest Jul–Sep 2026 at 62.1%, a swing of 38 points on roughly 60 flights a quarter. The twelve-month rate averages over that, so if you are flying in a weak quarter the quarter's own figure is the better guide.
- Jul–Sep 202530 flights100.0%
- Oct–Dec 202577 flights76.6%
- Jan–Mar 202663 flights93.5%
- Apr–Jun 202673 flights69.0%
- Jul–Sep 202658 flights62.1%
Scale runs 55% to 100%.
By weekday, DL 1551 did best on Friday at 89.8% on time and worst on Thursday at 67.3%. Each day rests on about 43 flights, so a gap of 23 points is worth noticing but could still narrow in another year.
Arrival by arrival
How late DL 1551 runs when it is late
DL 1551 often beats the schedule: 134 of 298 completed flights, 45%, arrived 15 minutes or more early. The 66 late arrivals split 24 under half an hour, 23 between 30 and 60 minutes, and 19 an hour or more.
- 15+ min early134 flights45.0%
- Within 15 min98 flights32.9%
- 15–29 min late24 flights8.1%
- 30–59 min late23 flights7.7%
- 1–2 hours late11 flights3.7%
- 2+ hours late8 flights2.7%
Scale runs 0% to 100%.
Share of 298 completed flights by arrival against schedule.
21 of 80 late departures made up the time and arrived on time, 26% of them. 7 flights left on time and still arrived late.
The worst days
Worst days for DL 1551
The latest arrival of the period was on 30 November 2025, 14 hours 22 minutes behind schedule; most of its delay minutes were filed as carrier-caused (crew, maintenance, fuelling, baggage). On three of the five worst days the largest share was filed as a late-arriving aircraft.
| Date | Arrived late by | Largest filed cause |
|---|---|---|
| 30 November 2025 | 14 hours 22 minutes | Carrier |
| 20 July 2026 | 3 hours 19 minutes | Late-arriving aircraft |
| 4 October 2025 | 3 hours 13 minutes | Late-arriving aircraft |
| 23 July 2026 | 2 hours 17 minutes | Carrier |
| 8 August 2026 | 2 hours 9 minutes | Late-arriving aircraft |
Delay causes
Why DL 1551 runs late
Carrier accounts for 49% of the 4,274 delay minutes carriers reported here, and the remaining four split what is left.
- 49%Carrier
- 44%Late-arriving aircraft
- 7%National Airspace System
44% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 4,274 reported delay minutes here, that single category outweighs weather by 44 to one. The split is drawn from 4,274 delay minutes reported on DL 1551.
Cancellations are rare at 0.33%, below the national 1.89% and low enough to earn the plus on the grade. Roughly one flight in 100 is called off; the risk here is arriving late, not not arriving.
Connections and routes
What a delay on this flight costs
6.4% of arrivals land an hour or more late, close to the national 8.3%, so a 60 to 75 minute layover is reasonable here while anything under 45 minutes is a bet. Most delays on this route last about an hour, which a normal layover absorbs.
The 954 miles between these two airports put this in the middle of the US network, around two and a half to three hours of block time. That is enough cruise to absorb a ten-minute late pushback and not enough to absorb thirty.
The same number turns up on two other city pairs in the data, including ATL to PNS (12) and PNS to ATL (9), but none flew often enough under DL 1551 to report a rate for. Carriers move flight numbers between routes, so the figures on this page apply to LAX to SEA only.
One caution: this is a thin sample. 301 flights over twelve months is enough to clear this site's floor but not enough to pin the rate down tightly, and a single bad week moves it by more than a point. Treat the grade as a rough reading.
What to do with this
Booking DL 1551
For a booking, DL 1551 is one of the weaker ways to fly LAX to SEA: 7 points below the route as a whole. If the schedule allows, compare it with the other departures listed on the route page before settling on this one.
Related
Where to go next
- LAX to SEA, every carrier and departure
- SEA to LAX, the return direction
- Delta Air Lines 2606 on the same route83.1%
- Delta Air Lines 2980 on the same route92.2%
- Delta Air Lines 2640 on the same route81.8%
- Delta Air Lines 1714 on the same route91.7%
- Delta Air Lines 1045 on the same route86.9%
- Alaska Airlines 1305 on the same route73.3%
- Los Angeles International (LAX) delay statistics
- Seattle-Tacoma International (SEA) delay statistics
- Delta Air Lines on-time record
- Every Delta Air Lines flight number with a record
- The most and least reliable flight numbers in the US
- Why the first flight of the morning is statistically safest
A flight number here means Delta Air Lines’s own number as it reports to the DOT. How the figures are computed is on the methodology page.
Source: US DOT Bureau of Transportation Statistics, on-time performance data, September 2025 to August 2026. Last updated ; recomputed monthly. How this data is collected.