Flight number record

DL 665

Delta Air Lines · Atlanta to Ontario

Route: ATL → ONT
Departs: 09:41
Flights: 365
Period: September 2025 to August 2026

Historical statistics for September 2025 to August 2026, not live status. For today’s DL 665, check with Delta Air Lines.

DL 665 earns a B. More than four flights in five arrive inside the 15-minute window the DOT uses to define an on-time arrival, which puts it 7 points better than the national rate of 77.3%. When something does go wrong the average delay runs roughly 50 minutes. That rests on 365 flights, with a median arrival 6 minutes early.

Set against the rest of the country, DL 665's record is 7 points better than the US average of 77.3%. That gap is worth roughly 67 fewer late arrivals for every thousand flights.

On time

84.0%

Arrivals under 15 minutes late, of 356 completed flights

Avg delay

51 min

Across delayed arrivals only, not all flights

Cancelled

2.47%

National rate is 1.89%

1 hour+ late

5.1%

National rate is 8.3%

These figures cover 365 flights between September 2025 and August 2026. The median arrival is 6 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 665 flies

DL 665 flies ATL to ONT without a single fixed slot. Its most common scheduled departure was 09:41, used on 38 of 365 flights.

Departs 09:4138 flights10.4%

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 09:41 departure sits in the 8am–11am window. Across every US flight scheduled in that window the on-time rate is 83.9%, and DL 665 runs level with that at 84.0%. Early departures usually start with an aircraft that has not flown yet that day, which is most of why the window does well.

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Against the route

DL 665 next to ATL to ONT

Every carrier on ATL to ONT combined arrived on time 74.2% of the time across 934 flights, so DL 665 is 10 points ahead of it. Across its whole network Delta Air Lines managed 81.1%, which this flight beats by 3 points.

DL 665 against its route and carrier
Compared with	Flights	On time	Avg delay	Cancelled	Grade
DL 665	365	84.0%	51 min	2.47%	B
All Delta Air Lines on ATL–ONT	934	74.2%	52 min	1.71%	C
All carriers on ATL–ONT	934	74.2%	52 min	1.71%	C
Delta Air Lines, whole network	1,039,517	81.1%	71 min	1.74%	B

Across the year

DL 665 quarter by quarter

DL 665 did not run the same all year. Its best quarter was Oct–Dec 2025 at 87.6% on time and its weakest Apr–Jun 2026 at 77.5%, a swing of 10 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 flights86.7%
Oct–Dec 202592 flights87.6%
Jan–Mar 202690 flights83.7%
Apr–Jun 202691 flights77.5%
Jul–Sep 202662 flights87.1%

Scale runs 70% to 95%.

By weekday, DL 665 ranged from 80.4% on Friday to 88.2% on Wednesday. With about 52 flights behind each day, a spread of 8 points is inside normal variation, so the day you fly is not worth changing for this flight.

Arrival by arrival

How late DL 665 runs when it is late

DL 665 often beats the schedule: 95 of 356 completed flights, 27%, arrived 15 minutes or more early. The 57 late arrivals split 26 under half an hour, 13 between 30 and 60 minutes, and 18 an hour or more.

15+ min early95 flights26.7%
Within 15 min204 flights57.3%
15–29 min late26 flights7.3%
30–59 min late13 flights3.7%
1–2 hours late14 flights3.9%
2+ hours late4 flights1.1%

Scale runs 0% to 100%.

Share of 356 completed flights by arrival against schedule.

12 of 52 late departures made up the time and arrived on time, 23% of them. 17 flights left on time and still arrived late.

The worst days

Worst days for DL 665

The latest arrival of the period was on 5 January 2026, 3 hours 13 minutes behind schedule; most of its delay minutes were filed as carrier-caused (crew, maintenance, fuelling, baggage). The same cause led on four of the five worst days.

The latest arrivals of DL 665 in the period
Date	Arrived late by	Largest filed cause
5 January 2026	3 hours 13 minutes	Carrier
14 November 2025	2 hours 55 minutes	Carrier
23 January 2026	2 hours 37 minutes	Carrier
22 November 2025	2 hours 26 minutes	Carrier
7 May 2026	1 hour 58 minutes	Late-arriving aircraft

Delay causes

Why DL 665 runs late

Carrier accounts for 56% of the 2,921 delay minutes carriers reported here, and the remaining four split what is left.

Carrier
56%
National Airspace System
27%
Late-arriving aircraft
14%
Extreme weather
2%

The largest share of delay minutes, 56%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. It accounts for 1,648 of the 2,921 delay minutes reported here. The split is drawn from 2,921 delay minutes reported on DL 665.

Cancellations sit at 2.47% against a national 1.89%, which is ordinary. Diversions add another 0.00%.

Connections and routes

What a delay on this flight costs

5.1% 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 roughly 50 minutes, which a normal layover absorbs.

At 1,900 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.

DL 665 is not only a ATL to ONT flight. It also flew ONT to ATL (365 flights, 83.9% on time) often enough to be scored on its own. Airlines attach one number to several legs of an aircraft's day, and each leg keeps its own record here, so check which city pair is on your booking before reading a rate.

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.

Other routes flown as DL 665
Also flown as	Flights	On time	Avg delay	Cancelled	Grade
ONT to ATL	365	83.9%	73 min	1.64%	B

What to do with this

Booking DL 665

For a booking, read DL 665 as 84.0% on time with 2.47% cancelled over 365 flights. Those are rates from the past twelve months, not a forecast for any particular 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, September 2025 to August 2026. Last updated 22 October 2026; recomputed monthly. How this data is collected.

Key figures