Flight number record

DL 1239

Delta Air Lines · Seattle to Salt Lake City

Route: SEA → SLC
Departs: 19:50
Flights: 256
Period: September 2025 to August 2026

Historical statistics for September 2025 to August 2026, not live status. For today’s DL 1239, check with Delta Air Lines.

DL 1239 lands a B+, 4 points better than the national rate of 77.3%. About one flight in five arrives 15 minutes late or worse, and those flights are late by about an hour on average. That rests on 256 flights, with a median arrival 9 minutes early.

On time

81.2%

Arrivals under 15 minutes late, of 255 completed flights

Avg delay

55 min

Across delayed arrivals only, not all flights

Cancelled

0.39%

National rate is 1.89%

1 hour+ late

6.7%

National rate is 8.3%

These figures cover 256 flights between September 2025 and August 2026. The median arrival is 9 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 1239 flies

DL 1239 flies SEA to SLC without a single fixed slot. Its most common scheduled departure was 19:50, used on 55 of 256 flights, with 19:35 (52 flights) and 19:00 (44 flights) next.

Departs 19:5055 flights21.5%
Departs 19:3552 flights20.3%
Departs 19:0044 flights17.2%

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 19:50 departure sits in the 5pm–8pm window. Across every US flight scheduled in that window the on-time rate is 68.0%, and DL 1239 runs 13 points better at 81.2%. 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 1239 next to SEA to SLC

Every carrier on SEA to SLC combined arrived on time 83.4% of the time across 4,098 flights, so DL 1239 is 2 points behind it. Delta flew 2,232 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 81.1%, close to this flight's figure.

DL 1239 against its route and carrier
Compared with	Flights	On time	Avg delay	Cancelled	Grade
DL 1239thin sample	256	81.2%	55 min	0.39%	B+
All Delta Air Lines on SEA–SLC	2,232	86.8%	59 min	0.49%	A+
All carriers on SEA–SLC	4,098	83.4%	49 min	0.78%	B+
Delta Air Lines, whole network	1,039,517	81.1%	71 min	1.74%	B

Across the year

DL 1239 quarter by quarter

DL 1239 did not run the same all year. Its best quarter was Oct–Dec 2025 at 88.0% on time and its weakest Apr–Jun 2026 at 71.8%, a swing of 16 points on roughly 64 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 202512 flights—
Oct–Dec 202550 flights88.0%
Jan–Mar 202682 flights86.4%
Apr–Jun 202671 flights71.8%
Jul–Sep 202641 flights75.6%

Scale runs 65% to 95%. Rows with fewer than 30 flights show a dash.

By weekday, DL 1239 did best on Sunday at 85.1% on time and worst on Friday at 68.9%. Each day rests on about 37 flights, so a gap of 16 points is worth noticing but could still narrow in another year.

Arrival by arrival

How late DL 1239 runs when it is late

DL 1239 often beats the schedule: 89 of 255 completed flights, 35%, arrived 15 minutes or more early. The 48 late arrivals split 18 under half an hour, 13 between 30 and 60 minutes, and 17 an hour or more.

15+ min early89 flights34.9%
Within 15 min118 flights46.3%
15–29 min late18 flights7.1%
30–59 min late13 flights5.1%
1–2 hours late12 flights4.7%
2+ hours late5 flights2.0%

Scale runs 0% to 100%.

Share of 255 completed flights by arrival against schedule.

10 of 53 late departures made up the time and arrived on time, 19% of them. Only 5 left on time and still arrived late.

The worst days

Worst days for DL 1239

The latest arrival of the period was on 12 April 2026, 2 hours 46 minutes behind schedule; most of its delay minutes were filed as a late-arriving aircraft. The same cause led on three of the five worst days.

The latest arrivals of DL 1239 in the period
Date	Arrived late by	Largest filed cause
12 April 2026	2 hours 46 minutes	Late-arriving aircraft
18 May 2026	2 hours 34 minutes	Carrier
27 December 2025	2 hours 21 minutes	Late-arriving aircraft
20 April 2026	2 hours 21 minutes	Late-arriving aircraft
4 January 2026	2 hours 8 minutes	Carrier

Delay causes

Why DL 1239 runs late

Carrier accounts for 58% of the 2,661 delay minutes carriers reported here, and the remaining four split what is left.

Carrier
58%
Late-arriving aircraft
34%
National Airspace System
7%
Extreme weather
2%

The largest share of delay minutes, 58%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. It accounts for 1,535 of the 2,661 delay minutes reported here. The split is drawn from 2,661 delay minutes reported on DL 1239.

Cancellations are rare at 0.39%, below the national 1.89% 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

6.7% 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 about an hour, which a normal layover absorbs.

The 689 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 256 flights under DL 1239 in the data flew SEA to SLC. 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. 256 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 1239

For a booking, read DL 1239 as 81.2% on time with 0.39% cancelled over 256 flights. Those are rates from the past twelve months, not a forecast for any particular 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, September 2025 to August 2026. Last updated 22 October 2026; recomputed monthly. How this data is collected.

Key figures