Flight number record
DL 870
Delta Air Lines · Seattle to Dallas-Fort Worth
- Route
- SEA → DFW
- Departs
- 17:55
- Flights
- 351
- Period
- July 2025 to June 2026
Historical statistics for July 2025 to June 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. About seven flights in ten arrive on time by the DOT's definition, 7 points worse than the national rate of 77.6%. The late ones land an hour and a half behind schedule. That rests on 351 flights, with a median arrival 3 minutes early.
The national on-time rate over the same period is 77.6%, so DL 870 runs 7 points behind the country as a whole. Across a thousand flights that is about 66 extra late arrivals.
Key figures
On time
71.0%
Arrivals under 15 minutes late, of 341 completed flights
Avg delay
85 min
Across delayed arrivals only, not all flights
Cancelled
2.28%
National rate is 1.81%
1 hour+ late
10.3%
National rate is 8.1%
These figures cover 351 flights between July 2025 and June 2026. Beyond the headline rate, 10.3% of arrivals land a full hour or more behind schedule. That is the number that wrecks a connection, and it is not visible in an on-time percentage alone.
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 198 of 351 flights, with 17:50 (56 flights) and 17:59 (36 flights) next. Carriers retime flights through the season, so the rates here blend slightly different positions in the aircraft's day.
- Departs 17:55198 flights56.4%
- Departs 17:5056 flights16.0%
- Departs 17:5936 flights10.3%
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 17:55 departure sits in the 5pm–8pm window. Across every US flight scheduled in that window the on-time rate is 68.2%, and DL 870 runs 3 points better at 71.0%. 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 870 next to SEA to DFW
Every carrier on SEA to DFW combined arrived on time 77.6% of the time across 5,233 flights, so DL 870 is 7 points behind it. Delta flew 712 flights on the same city pair under all its flight numbers, including this one, and those ran 75.1% on time. Across its whole network Delta Air Lines managed 81.6%, which this flight trails by 11 points.
| Compared with | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| DL 870thin sample | 351 | 71.0% | 85 min | 2.28% | C |
| All Delta Air Lines on SEA–DFW | 712 | 75.1% | 83 min | 1.69% | B |
| All carriers on SEA–DFW | 5,233 | 77.6% | 79 min | 2.04% | B |
| Delta Air Lines, whole network | 1,038,570 | 81.6% | 71 min | 1.62% | B |
Across the year
DL 870 quarter by quarter
DL 870 did not run the same all year. Its best quarter was Jan–Mar 2026 at 78.3% on time and its weakest Jul–Sep 2025 at 61.6%, a swing of 17 points on roughly 88 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 202586 flights61.6%
- Oct–Dec 202589 flights73.3%
- Jan–Mar 202689 flights78.3%
- Apr–Jun 202687 flights70.9%
Scale runs 55% to 85%. Rows with fewer than 30 flights show a dash.
By weekday, DL 870 did best on Tuesday at 82.0% on time and worst on Sunday at 59.2%. Each day rests on about 50 flights, so a gap of 23 points is worth noticing but could still narrow in another year.
Delay causes
Why DL 870 runs late
One category carries most of the weight here. Carrier accounts for 58% of the 8,377 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.
- 58%Carrier
- 34%Late-arriving aircraft
- 7%National Airspace System
- 1%Extreme weather
The largest share of delay minutes, 58%, 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 4,849 of the 8,377 delay minutes reported here. The split is drawn from 8,377 delay minutes reported on DL 870.
Cancellations sit at 2.28% against a national 1.81%, which is ordinary. Diversions add another 0.57%.
Connections and routes
What a delay on this flight costs
For anyone connecting, the number to weigh is not the on-time rate but the tail behind it. 10.3% of arrivals land a full hour or more behind schedule, against 8.1% nationally. A 45-minute layover does not survive that, and no amount of walking quickly changes it. Ninety minutes is the honest minimum here, and two hours if the onward flight is on a separate ticket.
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 351 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. 351 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, DL 870 is one of the weaker ways to fly SEA to DFW: 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
- SEA to DFW, every carrier and departure
- DFW to SEA, the return direction
- American Airlines 2748 on the same route93.7%
- American Airlines 767 on the same route66.7%
- American Airlines 1667 on the same route89.7%
- Alaska Airlines 424 on the same route78.2%
- American Airlines 707 on the same route79.6%
- Alaska Airlines 414 on the same route88.3%
- 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, July 2025 to June 2026. Last updated 15 September 2026; recomputed monthly. How this data is collected.