Flight number record
DL 2666
Delta Air Lines · Salt Lake City to St. Louis
- Route
- SLC → STL
- Departs
- 20:50
- Flights
- 354
- Period
- September 2025 to August 2026
Historical statistics for September 2025 to August 2026, not live status. For today’s DL 2666, check with Delta Air Lines.
DL 2666 lands a B+, 3 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 354 flights, with a median arrival 6 minutes early.
Key figures
On time
79.8%
Arrivals under 15 minutes late, of 352 completed flights
Avg delay
64 min
Across delayed arrivals only, not all flights
Cancelled
0.56%
National rate is 1.89%
1 hour+ late
8.2%
National rate is 8.3%
These figures cover 354 flights between September 2025 and August 2026. Beyond the headline rate, 8.2% of arrivals land a full hour or more behind schedule, against 8.3% nationally.
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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 97 of 354 flights, with 20:35 (80 flights) and 17:50 (40 flights) next.
- Departs 20:5097 flights27.4%
- Departs 20:3580 flights22.6%
- Departs 17:5040 flights11.3%
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 20:50 departure sits in the 8pm–5am window. Across every US flight scheduled in that window the on-time rate is 70.1%, and DL 2666 runs 10 points better at 79.8%. 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 2666 next to SLC to STL
Every carrier on SLC to STL combined arrived on time 83.7% of the time across 990 flights, so DL 2666 is 4 points behind it. Delta flew 981 flights on the same city pair under all its flight numbers, including this one, and those ran 83.7% on time. Across its whole network Delta Air Lines managed 81.1%, close to this flight's figure.
| Compared with | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| DL 2666thin sample | 354 | 79.8% | 64 min | 0.56% | B+ |
| All Delta Air Lines on SLC–STL | 981 | 83.7% | 58 min | 0.61% | B+ |
| All carriers on SLC–STL | 990 | 83.7% | 58 min | 0.61% | B+ |
| Delta Air Lines, whole network | 1,039,517 | 81.1% | 71 min | 1.74% | 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 Oct–Dec 2025 at 72.8%, a swing of 16 points on roughly 71 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 flights73.3%
- Oct–Dec 202582 flights72.8%
- Jan–Mar 202690 flights88.9%
- Apr–Jun 202691 flights80.2%
- Jul–Sep 202661 flights78.3%
Scale runs 65% to 95%.
By weekday, DL 2666 did best on Wednesday at 88.5% on time and worst on Sunday at 68.6%. Each day rests on about 51 flights, so a gap of 20 points is worth noticing but could still narrow in another year.
Arrival by arrival
How late DL 2666 runs when it is late
DL 2666 often beats the schedule: 103 of 352 completed flights, 29%, arrived 15 minutes or more early. The 71 late arrivals split 23 under half an hour, 19 between 30 and 60 minutes, and 29 an hour or more.
- 15+ min early103 flights29.3%
- Within 15 min178 flights50.6%
- 15–29 min late23 flights6.5%
- 30–59 min late19 flights5.4%
- 1–2 hours late19 flights5.4%
- 2+ hours late10 flights2.8%
Scale runs 0% to 100%.
Share of 352 completed flights by arrival against schedule.
22 of 88 late departures made up the time and arrived on time, 25% of them. Only 5 left on time and still arrived late.
The worst days
Worst days for DL 2666
The latest arrival of the period was on 4 December 2025, 3 hours 49 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 |
|---|---|---|
| 4 December 2025 | 3 hours 49 minutes | Late-arriving aircraft |
| 29 January 2026 | 3 hours 47 minutes | Carrier |
| 30 December 2025 | 3 hours 9 minutes | Carrier |
| 21 November 2025 | 2 hours 48 minutes | Carrier |
| 17 August 2026 | 2 hours 45 minutes | Carrier |
Delay causes
Why DL 2666 runs late
Carrier accounts for 60% of the 4,512 delay minutes carriers reported here, and the remaining four split what is left.
- 60%Carrier
- 32%Late-arriving aircraft
- 6%National Airspace System
- 1%Extreme weather
The largest share of delay minutes, 60%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. It accounts for 2,717 of the 4,512 delay minutes reported here. The split is drawn from 4,512 delay minutes reported on DL 2666.
Cancellations are rare at 0.56%, 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
8.2% 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 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.
Every one of the 354 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. 354 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, read DL 2666 as 79.8% on time with 0.56% cancelled over 354 flights. Those are rates from the past twelve months, not a forecast for any particular day.
Related
Where to go next
- SLC to STL, every carrier and departure
- STL to SLC, the return direction
- Delta Air Lines 2455 on the same route89.8%
- Salt Lake City International (SLC) delay statistics
- St. Louis Lambert International (STL) 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
- Why the first flight of the morning is statistically safest
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.