Flight number record
DL 1551
Delta Air Lines · Los Angeles to Seattle
- Route
- LAX → SEA
- Departs
- 19:59
- Flights
- 305
- Period
- July 2025 to June 2026
Historical statistics for July 2025 to June 2026, not live status. For today’s DL 1551, check with Delta Air Lines.
DL 1551 lands a B+, 4 points better than the national rate of 77.6%. About one flight in six arrives 15 minutes late or worse, and those flights are late by a little over an hour on average. That is a workable record, not a spotless one. That rests on 305 flights, with a median arrival 10 minutes early.
Set against the rest of the country, DL 1551's record is 4 points better than the US average of 77.6%. That gap is worth roughly 44 fewer late arrivals for every thousand flights.
Key figures
On time
82.0%
Arrivals under 15 minutes late, of 300 completed flights
Avg delay
71 min
Across delayed arrivals only, not all flights
Cancelled
0.66%
National rate is 1.81%
1 hour+ late
6.0%
National rate is 8.1%
These figures cover 305 flights between July 2025 and June 2026. The median arrival is 10 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.
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 83 of 305 flights, with 19:35 (32 flights) and 19:40 (31 flights) next. Carriers retime flights through the season, so the rates here blend slightly different positions in the aircraft's day.
- Departs 19:5983 flights27.2%
- Departs 19:3532 flights10.5%
- Departs 19:4031 flights10.2%
Scale runs 0% to 100%. Rows with fewer than 30 flights show a dash.
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 68.2%, and DL 1551 runs 14 points better at 82.0%. By that time of day most aircraft have flown several legs already, and whatever went wrong earlier is still in the schedule.
Against the route
DL 1551 next to LAX to SEA
Every carrier on LAX to SEA combined arrived on time 85.4% of the time across 7,424 flights, so DL 1551 is 3 points behind it. Delta flew 2,224 flights on the same city pair under all its flight numbers, including this one, and those ran 86.8% on time. Across its whole network Delta Air Lines managed 81.6%, close to this flight's figure.
| Compared with | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| DL 1551thin sample | 305 | 82.0% | 71 min | 0.66% | B+ |
| All Delta Air Lines on LAX–SEA | 2,224 | 86.8% | 76 min | 0.76% | A+ |
| All carriers on LAX–SEA | 7,424 | 85.4% | 64 min | 0.98% | A+ |
| Delta Air Lines, whole network | 1,038,570 | 81.6% | 71 min | 1.62% | B |
Across the year
DL 1551 quarter by quarter
DL 1551 did not run the same all year. Its best quarter was Jan–Mar 2026 at 93.5% on time and its weakest Apr–Jun 2026 at 69.0%, a swing of 25 points on roughly 76 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 202592 flights88.9%
- Oct–Dec 202577 flights76.6%
- Jan–Mar 202663 flights93.5%
- Apr–Jun 202673 flights69.0%
Scale runs 60% to 100%. Rows with fewer than 30 flights show a dash.
By weekday, DL 1551 did best on Friday at 89.8% on time and worst on Tuesday at 71.4%. Each day rests on about 44 flights, so a gap of 18 points is worth noticing but could still narrow in another year.
Delay causes
Why DL 1551 runs late
One category carries most of the weight here. Carrier accounts for 59% of the 3,805 delay minutes carriers reported, and the remaining four split what is left. The split is by minutes rather than by flights, so a few very long delays count for as much as many short ones.
- 59%Carrier
- 33%Late-arriving aircraft
- 8%National Airspace System
The largest share of delay minutes, 59%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. Unlike weather, that is a management outcome, and it is the category where the gap between two carriers on the same schedule is genuinely earned. It accounts for 2,251 of the 3,805 delay minutes reported here. The split is drawn from 3,805 delay minutes reported on DL 1551.
Cancellations are rare at 0.66%, below the national 1.81% 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
6.0% of arrivals land an hour or more late, close to the national 8.1%. That is the figure that decides a connection, and it says a 60 to 75 minute layover is reasonable here while anything under 45 minutes is a bet. Most delays on this route last a little over 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. It is also long enough that the aircraft usually flies three or four legs a day rather than six, which slows how fast delay compounds.
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. 305 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, read DL 1551 as 82.0% on time with 0.66% cancelled over 305 flights. Those are rates from the past twelve months, not a forecast for any particular day.
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 route84.8%
- Delta Air Lines 2980 on the same route91.9%
- Delta Air Lines 2640 on the same route82.4%
- Delta Air Lines 1714 on the same route92.5%
- Delta Air Lines 1045 on the same route88.8%
- Alaska Airlines 1301 on the same route86.8%
- 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, July 2025 to June 2026. Last updated 15 September 2026; recomputed monthly. How this data is collected.