Flight number record
DL 870
Delta Air Lines · Seattle to Dallas-Fort Worth
- Route
- SEA → DFW
- Departs
- 17:55
- Flights
- 356
- Period
- September 2025 to August 2026
Historical statistics for September 2025 to August 2026, not live status. For today’s DL 870, check with Delta Air Lines.
DL 870 sits in the middle of the pack with a C. Close to three flights in four arrive on time by the DOT's definition, 3 points worse than the national rate of 77.3%. The late ones land a little over an hour behind schedule. That rests on 356 flights, with a median arrival 4 minutes early.
Key figures
On time
74.0%
Arrivals under 15 minutes late, of 346 completed flights
Avg delay
75 min
Across delayed arrivals only, not all flights
Cancelled
2.25%
National rate is 1.89%
1 hour+ late
7.8%
National rate is 8.3%
These figures cover 356 flights between September 2025 and August 2026. The median arrival is 4 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 870 flies
DL 870 flies SEA to DFW without a single fixed slot. Its most common scheduled departure was 17:55, used on 229 of 356 flights, with 17:59 (36 flights) next.
- Departs 17:55229 flights64.3%
- Departs 17:5936 flights10.1%
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 17:55 departure sits in the 5pm–8pm window. Across every US flight scheduled in that window the on-time rate is 68.0%, and DL 870 runs 6 points better at 74.0%. 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 870 next to SEA to DFW
Every carrier on SEA to DFW combined arrived on time 78.0% of the time across 5,228 flights, so DL 870 is 4 points behind it. Delta flew 720 flights on the same city pair under all its flight numbers, including this one, and those ran 76.6% on time. Across its whole network Delta Air Lines managed 81.1%, which this flight trails by 7 points.
| Compared with | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| DL 870thin sample | 356 | 74.0% | 75 min | 2.25% | C |
| All Delta Air Lines on SEA–DFW | 720 | 76.6% | 75 min | 1.53% | B |
| All carriers on SEA–DFW | 5,228 | 78.0% | 75 min | 1.66% | B |
| Delta Air Lines, whole network | 1,039,517 | 81.1% | 71 min | 1.74% | B |
Across the year
DL 870 quarter by quarter
Quarter by quarter DL 870 held fairly steady: 76.7% in Jul–Sep 2025, 73.3% in Oct–Dec 2025, 78.3% in Jan–Mar 2026, 70.9% in Apr–Jun 2026 and 72.1% in Jul–Sep 2026. A spread of 7 points is about what a sample of this size moves on its own, so the annual figure is a fair summary.
- Jul–Sep 202530 flights76.7%
- Oct–Dec 202589 flights73.3%
- Jan–Mar 202689 flights78.3%
- Apr–Jun 202687 flights70.9%
- Jul–Sep 202661 flights72.1%
Scale runs 60% to 85%.
By weekday, DL 870 did best on Wednesday at 84.0% on time and worst on Sunday at 61.2%. Each day rests on about 51 flights, so a gap of 23 points is worth noticing but could still narrow in another year.
Arrival by arrival
How late DL 870 runs when it is late
DL 870 often beats the schedule: 112 of 346 completed flights, 32%, arrived 15 minutes or more early. The 90 late arrivals split 32 under half an hour, 31 between 30 and 60 minutes, and 27 an hour or more.
- 15+ min early112 flights32.4%
- Within 15 min144 flights41.6%
- 15–29 min late32 flights9.2%
- 30–59 min late31 flights9.0%
- 1–2 hours late10 flights2.9%
- 2+ hours late17 flights4.9%
Scale runs 0% to 100%.
Share of 346 completed flights by arrival against schedule.
17 of 91 late departures made up the time and arrived on time, 19% of them. 16 flights left on time and still arrived late.
The worst days
Worst days for DL 870
The latest arrival of the period was on 2 April 2026, 16 hours 18 minutes behind schedule; most of its delay minutes were filed as carrier-caused (crew, maintenance, fuelling, baggage). The same cause led on three of the five worst days.
| Date | Arrived late by | Largest filed cause |
|---|---|---|
| 2 April 2026 | 16 hours 18 minutes | Carrier |
| 12 June 2026 | 5 hours 11 minutes | Late-arriving aircraft |
| 9 December 2025 | 4 hours 58 minutes | Carrier |
| 5 October 2025 | 3 hours 57 minutes | Late-arriving aircraft |
| 28 April 2026 | 3 hours 52 minutes | Carrier |
Delay causes
Why DL 870 runs late
Carrier accounts for 54% of the 6,770 delay minutes carriers reported here, and the remaining four split what is left.
- 54%Carrier
- 37%Late-arriving aircraft
- 8%National Airspace System
- 1%Extreme weather
37% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 6,770 reported delay minutes here, that single category outweighs weather by 32 to one. The split is drawn from 6,770 delay minutes reported on DL 870.
Cancellations sit at 2.25% against a national 1.89%, which is ordinary. Diversions add another 0.56%.
Connections and routes
What a delay on this flight costs
7.8% 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 a little over an hour, which a normal layover absorbs.
At 1,660 miles this is transcontinental flying, and long routes get a quiet structural advantage. Scheduled block time on a flight this length carries more padding in absolute minutes, so a twenty-minute late departure often still becomes an on-time arrival. Read the on-time rate here as slightly flattering next to a short-haul route with the same operational quality.
Every one of the 356 flights under DL 870 in the data flew SEA to DFW. The number was not reused on any other city pair, which makes this a clean record of one route.
One caution: this is a thin sample. 356 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 870
For a booking, read DL 870 as 74.0% on time with 2.25% cancelled over 356 flights. Those are rates from the past twelve months, not a forecast for any particular day.
Related
Where to go next
- SEA to DFW, every carrier and departure
- DFW to SEA, the return direction
- American Airlines 2748 on the same route94.0%
- American Airlines 767 on the same route67.6%
- American Airlines 1667 on the same route88.4%
- American Airlines 707 on the same route76.8%
- Alaska Airlines 414 on the same route90.9%
- Alaska Airlines 424 on the same route78.9%
- Seattle-Tacoma International (SEA) delay statistics
- Dallas/Fort Worth International (DFW) 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.