Flight number record

DL 663

Delta Air Lines · Atlanta to Salt Lake City

Route: ATL → SLC
Departs: 11:55
Flights: 365
Period: July 2025 to June 2026

Historical statistics for July 2025 to June 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 10 points better than the national rate of 77.6%. When something does go wrong the average delay runs about 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 10 points better than the US average of 77.6%. That gap is worth roughly 100 fewer late arrivals for every thousand flights.

On time

87.6%

Arrivals under 15 minutes late, of 363 completed flights

Avg delay

56 min

Across delayed arrivals only, not all flights

Cancelled

0.55%

National rate is 1.81%

1 hour+ late

4.4%

National rate is 8.1%

These figures cover 365 flights between July 2025 and June 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.

Schedule

When DL 663 flies

DL 663 flies ATL to SLC without a single fixed slot. Its most common scheduled departure was 11:55, used on 90 of 365 flights, with 11:59 (57 flights) and 11:58 (56 flights) next. Carriers retime flights through the season, so the rates here blend slightly different positions in the aircraft's day.

Departs 11:5590 flights24.7%
Departs 11:5957 flights15.6%
Departs 11:5856 flights15.3%

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 11:55 departure sits in the 11am–2pm window. Across every US flight scheduled in that window the on-time rate is 78.8%, and DL 663 runs 9 points better at 87.6%. Midday slots inherit some of the morning's delays without yet carrying the full weight of the evening's.

Against the route

DL 663 next to ATL to SLC

Every carrier on ATL to SLC combined arrived on time 83.0% 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 83.0% on time. Across its whole network Delta Air Lines managed 81.6%, which this flight beats by 6 points.

DL 663 against its route and carrier
Compared with	Flights	On time	Avg delay	Cancelled	Grade
DL 663	365	87.6%	56 min	0.55%	A+
All Delta Air Lines on ATL–SLC	2,959	83.0%	60 min	0.41%	B+
All carriers on ATL–SLC	2,965	83.0%	60 min	0.40%	B+
Delta Air Lines, whole network	1,038,570	81.6%	71 min	1.62%	B

Across the year

DL 663 quarter by quarter

Quarter by quarter DL 663 held fairly steady: 90.1% in Jul–Sep 2025, 90.2% in Oct–Dec 2025, 83.1% in Jan–Mar 2026 and 86.8% in Apr–Jun 2026. A spread of 7 points is about what a sample of this size moves on its own, so the annual figure is a fair summary.

Jul–Sep 202592 flights90.1%
Oct–Dec 202592 flights90.2%
Jan–Mar 202690 flights83.1%
Apr–Jun 202691 flights86.8%

Scale runs 75% to 95%. Rows with fewer than 30 flights show a dash.

By weekday, DL 663 ranged from 82.4% on Saturday to 92.3% on Wednesday. With about 52 flights behind each day, a spread of 10 points is inside normal variation, so the day you fly is not worth changing for this flight.

Delay causes

Why DL 663 runs late

One category carries most of the weight here. Carrier accounts for 57% of the 2,509 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
57%
Late-arriving aircraft
25%
National Airspace System
13%
Extreme weather
5%

The largest share of delay minutes, 57%, 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 1,441 of the 2,509 delay minutes reported here. The split is drawn from 2,509 delay minutes reported on DL 663.

Cancellations are rare at 0.55%, 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 4.4% 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.

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: 87.6% on time and 0.55% 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