Flight number record
DL 1731
Delta Air Lines · Denver to Seattle
- Route
- DEN → SEA
- Departs
- 06:30
- Flights
- 364
- Period
- September 2025 to August 2026
Historical statistics for September 2025 to August 2026, not live status. For today’s DL 1731, check with Delta Air Lines.
DL 1731 earns an A. Close to nine flights in ten arrive inside the 15-minute window the DOT uses to define an on-time arrival, which puts it 12 points better than the national rate of 77.3%. When something does go wrong the average delay runs an hour and a half. That rests on 364 flights, with a median arrival 12 minutes early.
Set against the rest of the country, DL 1731's record is 12 points better than the US average of 77.3%. That gap is worth roughly 121 fewer late arrivals for every thousand flights.
Key figures
On time
89.4%
Arrivals under 15 minutes late, of 359 completed flights
Avg delay
86 min
Across delayed arrivals only, not all flights
Cancelled
1.37%
National rate is 1.89%
1 hour+ late
3.1%
National rate is 8.3%
These figures cover 364 flights between September 2025 and August 2026. The median arrival is 12 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 1731 flies
DL 1731 flies DEN to SEA without a single fixed slot. Its most common scheduled departure was 06:30, used on 93 of 364 flights, with 06:05 (88 flights) and 06:55 (44 flights) next.
- Departs 06:3093 flights25.5%
- Departs 06:0588 flights24.2%
- Departs 06:5544 flights12.1%
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 06:30 departure sits in the 5am–8am window. Across every US flight scheduled in that window the on-time rate is 89.3%, and DL 1731 runs level with that at 89.4%. Early departures usually start with an aircraft that has not flown yet that day, which is most of why the window does well.
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Against the route
DL 1731 next to DEN to SEA
Every carrier on DEN to SEA combined arrived on time 74.5% of the time across 6,328 flights, so DL 1731 is 15 points ahead of it. Delta flew 868 flights on the same city pair under all its flight numbers, including this one, and those ran 78.5% on time. Across its whole network Delta Air Lines managed 81.1%, which this flight beats by 8 points.
| Compared with | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| DL 1731thin sample | 364 | 89.4% | 86 min | 1.37% | A |
| All Delta Air Lines on DEN–SEA | 868 | 78.5% | 86 min | 0.92% | B+ |
| All carriers on DEN–SEA | 6,328 | 74.5% | 58 min | 0.60% | C+ |
| Delta Air Lines, whole network | 1,039,517 | 81.1% | 71 min | 1.74% | B |
Across the year
DL 1731 quarter by quarter
DL 1731 did not run the same all year. Its best quarter was Jul–Sep 2025 at 100.0% on time and its weakest Oct–Dec 2025 at 76.4%, a swing of 24 points on roughly 73 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 202591 flights76.4%
- Jan–Mar 202690 flights89.9%
- Apr–Jun 202691 flights98.9%
- Jul–Sep 202662 flights88.5%
Scale runs 70% to 100%.
By weekday, DL 1731 did best on Tuesday at 96.1% on time and worst on Sunday at 78.8%. Each day rests on about 52 flights, so a gap of 17 points is worth noticing but could still narrow in another year.
Arrival by arrival
How late DL 1731 runs when it is late
DL 1731 often beats the schedule: 159 of 359 completed flights, 44%, arrived 15 minutes or more early. Most of the lateness is short. 23 of the 38 late arrivals were under half an hour behind, and 11 reached an hour or more.
- 15+ min early159 flights44.3%
- Within 15 min162 flights45.1%
- 15–29 min late23 flights6.4%
- 30–59 min late4 flights1.1%
- 1–2 hours late5 flights1.4%
- 2+ hours late6 flights1.7%
Scale runs 0% to 100%.
Share of 359 completed flights by arrival against schedule.
3 of 22 late departures made up the time and arrived on time, 14% of them. In the other direction, 19 flights left on time yet arrived 15 minutes late or more, so that delay built up after pushback: in the air, in a holding pattern or on the ground at SEA.
The worst days
Worst days for DL 1731
The latest arrival of the period was on 12 December 2025, 14 hours 27 minutes behind schedule; most of its delay minutes were filed as a late-arriving aircraft. On four of the five worst days the largest share was filed as carrier-caused (crew, maintenance, fuelling, baggage).
| Date | Arrived late by | Largest filed cause |
|---|---|---|
| 12 December 2025 | 14 hours 27 minutes | Late-arriving aircraft |
| 20 November 2025 | 6 hours 36 minutes | Carrier |
| 23 May 2026 | 5 hours 59 minutes | Carrier |
| 20 October 2025 | 3 hours 33 minutes | Carrier |
| 16 November 2025 | 3 hours 8 minutes | Carrier |
Delay causes
Why DL 1731 runs late
Carrier accounts for 61% of the 3,256 delay minutes carriers reported here, and the remaining four split what is left.
- 61%Carrier
- 26%Late-arriving aircraft
- 13%National Airspace System
The largest share of delay minutes, 61%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. It accounts for 1,985 of the 3,256 delay minutes reported here. The split is drawn from 3,256 delay minutes reported on DL 1731.
Cancellations sit at 1.37% against a national 1.89%, which is ordinary. Diversions add another 0.00%.
Connections and routes
What a delay on this flight costs
Badly late arrivals are rare here: only 3.1% land an hour or more behind schedule, against 8.3% nationally. Connections built on this flight are about as safe as US domestic connections get, though a cancelled flight still ignores every layover you give it.
The 1,024 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.
Every one of the 364 flights under DL 1731 in the data flew DEN to SEA. 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. 364 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 1731
For a booking, DL 1731 has one of the better records a US domestic flight can show: 89.4% on time and 1.37% cancelled. That is a base rate, not a promise about any single day.
Related
Where to go next
- DEN to SEA, every carrier and departure
- SEA to DEN, the return direction
- United Airlines 2271 on the same route91.9%
- Alaska Airlines 643 on the same route89.5%
- United Airlines 2013 on the same route77.9%
- United Airlines 1424 on the same route85.7%
- Denver International (DEN) 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
- Worst months to fly in the US, ranked by the data
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.