Flight number record

DL 2666

Delta Air Lines · Salt Lake City to St. Louis

Route: SLC → STL
Departs: 20:50
Flights: 355
Period: July 2025 to June 2026

Historical statistics for July 2025 to June 2026, not live status. For today’s DL 2666, check with Delta Air Lines.

DL 2666 lands a B+, level with the national rate of 77.6%. Roughly one flight in five arrives 15 minutes late or worse, and those flights are late by about an hour on average. That is a workable record, not a spotless one. That rests on 355 flights, with a median arrival 8 minutes early.

On time

78.2%

Arrivals under 15 minutes late, of 354 completed flights

Avg delay

61 min

Across delayed arrivals only, not all flights

Cancelled

0.28%

National rate is 1.81%

1 hour+ late

8.8%

National rate is 8.1%

These figures cover 355 flights between July 2025 and June 2026. Beyond the headline rate, 8.8% 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 2666 flies

DL 2666 flies SLC to STL without a single fixed slot. Its most common scheduled departure was 20:50, used on 100 of 355 flights, with 20:35 (80 flights) and 17:50 (40 flights) next. Carriers retime flights through the season, so the rates here blend slightly different positions in the aircraft's day.

Departs 20:50100 flights28.2%
Departs 20:3580 flights22.5%
Departs 17:5040 flights11.3%

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 20:50 departure sits in the 8pm–5am window. Across every US flight scheduled in that window the on-time rate is 70.5%, and DL 2666 runs 8 points better at 78.2%. 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 2666 next to SLC to STL

Every carrier on SLC to STL combined arrived on time 83.9% of the time across 989 flights, so DL 2666 is 6 points behind it. Delta flew 978 flights on the same city pair under all its flight numbers, including this one, and those ran 83.8% on time. Across its whole network Delta Air Lines managed 81.6%, which this flight trails by 3 points.

DL 2666 against its route and carrier
Compared with	Flights	On time	Avg delay	Cancelled	Grade
DL 2666thin sample	355	78.2%	61 min	0.28%	B+
All Delta Air Lines on SLC–STL	978	83.8%	63 min	0.51%	B+
All carriers on SLC–STL	989	83.9%	63 min	0.51%	B+
Delta Air Lines, whole network	1,038,570	81.6%	71 min	1.62%	B

Across the year

DL 2666 quarter by quarter

DL 2666 did not run the same all year. Its best quarter was Jan–Mar 2026 at 88.9% on time and its weakest Jul–Sep 2025 at 70.7%, a swing of 18 points on roughly 89 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 flights70.7%
Oct–Dec 202582 flights72.8%
Jan–Mar 202690 flights88.9%
Apr–Jun 202691 flights80.2%

Scale runs 60% to 95%. Rows with fewer than 30 flights show a dash.

By weekday, DL 2666 did best on Monday at 86.5% on time and worst on Sunday at 67.3%. Each day rests on about 51 flights, so a gap of 19 points is worth noticing but could still narrow in another year.

Delay causes

Why DL 2666 runs late

One category carries most of the weight here. Carrier accounts for 65% of the 4,730 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
65%
Late-arriving aircraft
27%
National Airspace System
7%
Extreme weather
1%

The largest share of delay minutes, 65%, 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 3,068 of the 4,730 delay minutes reported here. The split is drawn from 4,730 delay minutes reported on DL 2666.

Cancellations are rare at 0.28%, 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

8.8% of arrivals land an hour or more late, close to the national 8.1%. That is the figure that decides a connection, and it says 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 1,156 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 355 flights under DL 2666 in the data flew SLC to STL. 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. 355 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 2666

For a booking, DL 2666 is one of the weaker ways to fly SLC to STL: 6 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.

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