Flight number record

DL 1128

Delta Air Lines · Seattle to Salt Lake City

Route: SEA → SLC
Departs: 05:30
Flights: 365
Period: July 2025 to June 2026

Historical statistics for July 2025 to June 2026, not live status. For today’s DL 1128, check with Delta Air Lines.

DL 1128 earns an A+. Nearly every flight arrives inside the 15-minute window the DOT uses to define an on-time arrival, which puts it 17 points better than the national rate of 77.6%. When something does go wrong the average delay runs a little over an hour. That rests on 365 flights, with a median arrival 14 minutes early.

Set against the rest of the country, DL 1128's record is 17 points better than the US average of 77.6%. That gap is worth roughly 166 fewer late arrivals for every thousand flights.

On time

94.2%

Arrivals under 15 minutes late, of 364 completed flights

Avg delay

76 min

Across delayed arrivals only, not all flights

Cancelled

0.27%

National rate is 1.81%

1 hour+ late

2.2%

National rate is 8.1%

These figures cover 365 flights between July 2025 and June 2026. The median arrival is 14 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 1128 flies

DL 1128 flies SEA to SLC without a single fixed slot. Its most common scheduled departure was 05:30, used on 220 of 365 flights, with 05:25 (101 flights) next. Carriers retime flights through the season, so the rates here blend slightly different positions in the aircraft's day.

Departs 05:30220 flights60.3%
Departs 05:25101 flights27.7%

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 05:30 departure sits in the 5am–8am window. Across every US flight scheduled in that window the on-time rate is 89.3%, and DL 1128 runs 5 points better at 94.2%. 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 1128 next to SEA to SLC

Every carrier on SEA to SLC combined arrived on time 83.6% of the time across 4,107 flights, so DL 1128 is 11 points ahead of it. Delta flew 2,219 flights on the same city pair under all its flight numbers, including this one, and those ran 87.0% on time. Across its whole network Delta Air Lines managed 81.6%, which this flight beats by 13 points.

DL 1128 against its route and carrier
Compared with	Flights	On time	Avg delay	Cancelled	Grade
DL 1128	365	94.2%	76 min	0.27%	A+
All Delta Air Lines on SEA–SLC	2,219	87.0%	58 min	0.54%	A+
All carriers on SEA–SLC	4,107	83.6%	50 min	0.93%	B+
Delta Air Lines, whole network	1,038,570	81.6%	71 min	1.62%	B

Across the year

DL 1128 quarter by quarter

DL 1128 did not run the same all year. Its best quarter was Apr–Jun 2026 at 98.9% on time and its weakest Jan–Mar 2026 at 85.4%, a swing of 14 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 flights96.7%
Oct–Dec 202592 flights95.7%
Jan–Mar 202690 flights85.4%
Apr–Jun 202691 flights98.9%

Scale runs 75% to 100%. Rows with fewer than 30 flights show a dash.

By weekday, DL 1128 ranged from 90.6% on Tuesday to 96.2% on Thursday. With about 52 flights behind each day, a spread of 6 points is inside normal variation, so the day you fly is not worth changing for this flight.

Delay causes

Why DL 1128 runs late

One category carries most of the weight here. Carrier accounts for 88% of the 1,602 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
88%
National Airspace System
12%

The largest share of delay minutes, 88%, 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 1,411 of the 1,602 delay minutes reported here. The split is drawn from 1,602 delay minutes reported on DL 1128.

Cancellations are rare at 0.27%, below the national 1.81% 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

Badly late arrivals are rare here: only 2.2% 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 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. 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 365 flights under DL 1128 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. 365 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 1128

For a booking, DL 1128 has one of the better records a US domestic flight can show: 94.2% on time and 0.27% 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