Flight number record

DL 660

Delta Air Lines · Atlanta to Salt Lake City

Route: ATL → SLC
Departs: 19:30
Flights: 361
Period: July 2025 to June 2026

Historical statistics for July 2025 to June 2026, not live status. For today’s DL 660, check with Delta Air Lines.

DL 660 lands a B+, about a point worse than the national rate of 77.6%. About one flight in four 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 361 flights, with a median arrival 4 minutes early.

On time

76.4%

Arrivals under 15 minutes late, of 360 completed flights

Avg delay

56 min

Across delayed arrivals only, not all flights

Cancelled

0.28%

National rate is 1.81%

1 hour+ late

8.1%

National rate is 8.1%

These figures cover 361 flights between July 2025 and June 2026. Beyond the headline rate, 8.1% 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 660 flies

DL 660 flies ATL to SLC without a single fixed slot. Its most common scheduled departure was 19:30, used on 67 of 361 flights, with 19:45 (61 flights) and 19:50 (45 flights) next. Carriers retime flights through the season, so the rates here blend slightly different positions in the aircraft's day.

Departs 19:3067 flights18.6%
Departs 19:4561 flights16.9%
Departs 19:5045 flights12.5%

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 19:30 departure sits in the 5pm–8pm window. Across every US flight scheduled in that window the on-time rate is 68.2%, and DL 660 runs 8 points better at 76.4%. 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 660 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 660 is 7 points behind 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 trails by 5 points.

DL 660 against its route and carrier
Compared with	Flights	On time	Avg delay	Cancelled	Grade
DL 660thin sample	361	76.4%	56 min	0.28%	B+
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 660 quarter by quarter

DL 660 did not run the same all year. Its best quarter was Jan–Mar 2026 at 84.3% on time and its weakest Jul–Sep 2025 at 70.7%, a swing of 14 points on roughly 90 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 202588 flights71.6%
Jan–Mar 202690 flights84.3%
Apr–Jun 202691 flights79.1%

Scale runs 60% to 90%. Rows with fewer than 30 flights show a dash.

By weekday, DL 660 did best on Tuesday at 86.8% on time and worst on Thursday at 70.6%. Each day rests on about 52 flights, so a gap of 16 points is worth noticing but could still narrow in another year.

Delay causes

Why DL 660 runs late

One category carries most of the weight here. Carrier accounts for 54% of the 4,769 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
54%
Late-arriving aircraft
23%
National Airspace System
15%
Extreme weather
8%

The largest share of delay minutes, 54%, 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 2,597 of the 4,769 delay minutes reported here. The split is drawn from 4,769 delay minutes reported on DL 660.

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

8.1% 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.

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 361 flights under DL 660 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. 361 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 660

For a booking, DL 660 is one of the weaker ways to fly ATL to SLC: 7 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