Flight number record

DL 1731

Delta Air Lines · Denver to Seattle

Route: DEN → SEA
Departs: 06:05
Flights: 364
Period: July 2025 to June 2026

Historical statistics for July 2025 to June 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 77.6%. 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 77.6%. That gap is worth roughly 118 fewer late arrivals for every thousand flights.

On time

89.4%

Arrivals under 15 minutes late, of 360 completed flights

Avg delay

99 min

Across delayed arrivals only, not all flights

Cancelled

1.10%

National rate is 1.81%

1 hour+ late

3.1%

National rate is 8.1%

These figures cover 364 flights between July 2025 and June 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.

Schedule

When DL 1731 flies

DL 1731 flies DEN to SEA without a single fixed slot. Its most common scheduled departure was 06:05, used on 88 of 364 flights, with 06:30 (66 flights) and 06:50 (66 flights) next. Carriers retime flights through the season, so the rates here blend slightly different positions in the aircraft's day.

Departs 06:0588 flights24.2%
Departs 06:3066 flights18.1%
Departs 06:5066 flights18.1%

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 06:05 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.

Against the route

DL 1731 next to DEN to SEA

Every carrier on DEN to SEA combined arrived on time 73.9% of the time across 6,309 flights, so DL 1731 is 16 points ahead of it. Delta flew 868 flights on the same city pair under all its flight numbers, including this one, and those ran 79.2% on time. Across its whole network Delta Air Lines managed 81.6%, which this flight beats by 8 points.

DL 1731 against its route and carrier
Compared with	Flights	On time	Avg delay	Cancelled	Grade
DL 1731thin sample	364	89.4%	99 min	1.10%	A
All Delta Air Lines on DEN–SEA	868	79.2%	89 min	0.92%	B+
All carriers on DEN–SEA	6,309	73.9%	57 min	0.76%	C+
Delta Air Lines, whole network	1,038,570	81.6%	71 min	1.62%	B

Across the year

DL 1731 quarter by quarter

DL 1731 did not run the same all year. Its best quarter was Apr–Jun 2026 at 98.9% on time and its weakest Oct–Dec 2025 at 76.4%, a swing of 23 points on roughly 91 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 flights92.4%
Oct–Dec 202591 flights76.4%
Jan–Mar 202690 flights89.9%
Apr–Jun 202691 flights98.9%

Scale runs 70% to 100%. Rows with fewer than 30 flights show a dash.

By weekday, DL 1731 did best on Tuesday at 100.0% on time and worst on Sunday at 80.8%. Each day rests on about 52 flights, so a gap of 19 points is worth noticing but could still narrow in another year.

Delay causes

Why DL 1731 runs late

One category carries most of the weight here. Carrier accounts for 49% of the 3,771 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.

Carrier
49%
Late-arriving aircraft
35%
National Airspace System
12%
Extreme weather
4%

35% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. That is a cascade, and cascades start small and grow through the day. Across 3,771 reported delay minutes here, that single category outweighs weather by 8 to one. It is the strongest argument for booking the first departure of the morning, when the aircraft has been sitting at the gate overnight with nothing to inherit. The split is drawn from 3,771 delay minutes reported on DL 1731.

Cancellations sit at 1.10% against a national 1.81%, 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 8.1% 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. 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.

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 1.10% cancelled. That is a base rate, not a promise about any single day.

Where to go next

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.

Key figures