Flight number record
DL 663
Delta Air Lines · Atlanta to Salt Lake City
- Route
- ATL → SLC
- Departs
- 11:56
- Flights
- 365
- Period
- September 2025 to August 2026
Historical statistics for September 2025 to August 2026, not live status. For today’s DL 663, check with Delta Air Lines.
DL 663 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 11 points better than the national rate of 77.3%. When something does go wrong the average delay runs a little over an hour. That rests on 365 flights, with a median arrival 7 minutes early.
Set against the rest of the country, DL 663's record is 11 points better than the US average of 77.3%. That gap is worth roughly 106 fewer late arrivals for every thousand flights.
Key figures
On time
87.9%
Arrivals under 15 minutes late, of 364 completed flights
Avg delay
72 min
Across delayed arrivals only, not all flights
Cancelled
0.27%
National rate is 1.89%
1 hour+ late
5.2%
National rate is 8.3%
These figures cover 365 flights between September 2025 and August 2026. The median arrival is 7 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 663 flies
DL 663 flies ATL to SLC without a single fixed slot. Its most common scheduled departure was 11:56, used on 74 of 365 flights, with 11:59 (57 flights) and 11:58 (56 flights) next.
- Departs 11:5674 flights20.3%
- Departs 11:5957 flights15.6%
- Departs 11:5856 flights15.3%
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 11:56 departure sits in the 11am–2pm window. Across every US flight scheduled in that window the on-time rate is 78.3%, and DL 663 runs 10 points better at 87.9%. Midday slots inherit some of the morning's delays without yet carrying the full weight of the evening's.
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Against the route
DL 663 next to ATL to SLC
Every carrier on ATL to SLC combined arrived on time 82.7% of the time across 2,965 flights, so DL 663 is 5 points ahead of it. Delta flew 2,959 flights on the same city pair under all its flight numbers, including this one, and those ran 82.7% on time. Across its whole network Delta Air Lines managed 81.1%, which this flight beats by 7 points.
| Compared with | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| DL 663 | 365 | 87.9% | 72 min | 0.27% | A+ |
| All Delta Air Lines on ATL–SLC | 2,959 | 82.7% | 60 min | 0.44% | B+ |
| All carriers on ATL–SLC | 2,965 | 82.7% | 60 min | 0.44% | B+ |
| Delta Air Lines, whole network | 1,039,517 | 81.1% | 71 min | 1.74% | B |
Across the year
DL 663 quarter by quarter
DL 663 did not run the same all year. Its best quarter was Jul–Sep 2025 at 100.0% on time and its weakest Jan–Mar 2026 at 83.1%, a swing of 17 points on roughly 73 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 flights100.0%
- Oct–Dec 202592 flights90.2%
- Jan–Mar 202690 flights83.1%
- Apr–Jun 202691 flights86.8%
- Jul–Sep 202662 flights87.1%
Scale runs 75% to 100%.
By weekday, DL 663 ranged from 84.9% on Monday to 92.3% on Friday. With about 52 flights behind each day, a spread of 7 points is inside normal variation, so the day you fly is not worth changing for this flight.
Arrival by arrival
How late DL 663 runs when it is late
DL 663 often beats the schedule: 118 of 364 completed flights, 32%, arrived 15 minutes or more early. The 44 late arrivals split 15 under half an hour, 10 between 30 and 60 minutes, and 19 an hour or more.
- 15+ min early118 flights32.4%
- Within 15 min202 flights55.5%
- 15–29 min late15 flights4.1%
- 30–59 min late10 flights2.7%
- 1–2 hours late12 flights3.3%
- 2+ hours late7 flights1.9%
Scale runs 0% to 100%.
Share of 364 completed flights by arrival against schedule.
A late pushback is often recovered here: of 54 departures that left 15 minutes late or more, 17 still arrived on time. Only 7 left on time and still arrived late.
The worst days
Worst days for DL 663
The latest arrival of the period was on 24 July 2026, 7 hours 15 minutes behind schedule; most of its delay minutes were filed as carrier-caused (crew, maintenance, fuelling, baggage). The same cause led on five of the five worst days.
| Date | Arrived late by | Largest filed cause |
|---|---|---|
| 24 July 2026 | 7 hours 15 minutes | Carrier |
| 4 August 2026 | 3 hours 14 minutes | Carrier |
| 16 July 2026 | 3 hours 1 minute | Carrier |
| 10 August 2026 | 2 hours 44 minutes | Carrier |
| 18 February 2026 | 2 hours 25 minutes | Carrier |
Delay causes
Why DL 663 runs late
Carrier accounts for 72% of the 3,164 delay minutes carriers reported here, and the remaining four split what is left.
- 72%Carrier
- 17%Late-arriving aircraft
- 10%National Airspace System
- 1%Extreme weather
The largest share of delay minutes, 72%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. It accounts for 2,292 of the 3,164 delay minutes reported here. The split is drawn from 3,164 delay minutes reported on DL 663.
Cancellations are rare at 0.27%, 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
5.2% 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 a little over an hour, which a normal layover absorbs.
At 1,590 miles this is transcontinental flying, and long routes get a quiet structural advantage. Scheduled block time on a flight this length carries more padding in absolute minutes, so a twenty-minute late departure often still becomes an on-time arrival. Read the on-time rate here as slightly flattering next to a short-haul route with the same operational quality.
Every one of the 365 flights under DL 663 in the data flew ATL 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 663
For a booking, DL 663 has one of the better records a US domestic flight can show: 87.9% on time and 0.27% cancelled. That is a base rate, not a promise about any single day.
Related
Where to go next
- ATL to SLC, every carrier and departure
- SLC to ATL, the return direction
- Delta Air Lines 830 on the same route87.8%
- Delta Air Lines 387 on the same route90.3%
- Delta Air Lines 423 on the same route85.6%
- Delta Air Lines 653 on the same route79.4%
- Delta Air Lines 526 on the same route79.6%
- Delta Air Lines 660 on the same route75.0%
- Hartsfield-Jackson Atlanta International (ATL) delay statistics
- Salt Lake City International (SLC) 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
- Worst months to fly in the US, ranked by the data
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.