Flight number record

DL 665

Delta Air Lines · Atlanta to Ontario

Route: ATL → ONT
Departs: 09:15
Flights: 365
Period: July 2025 to June 2026

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

DL 665 earns an A. More than four flights in five arrive inside the 15-minute window the DOT uses to define an on-time arrival, which puts it 8 points better than the national rate of 77.6%. When something does go wrong the average delay runs roughly 55 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 8 points better than the US average of 77.6%. That gap is worth roughly 78 fewer late arrivals for every thousand flights.

On time

85.4%

Arrivals under 15 minutes late, of 356 completed flights

Avg delay

54 min

Across delayed arrivals only, not all flights

Cancelled

2.47%

National rate is 1.81%

1 hour+ late

5.1%

National rate is 8.1%

These figures cover 365 flights between July 2025 and June 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.

Schedule

When DL 665 flies

DL 665 flies ATL to ONT without a single fixed slot. Its most common scheduled departure was 09:15, used on 58 of 365 flights, with 09:20 (54 flights) and 09:41 (38 flights) next. Carriers retime flights through the season, so the rates here blend slightly different positions in the aircraft's day.

Departs 09:1558 flights15.9%
Departs 09:2054 flights14.8%
Departs 09:4138 flights10.4%

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 09:15 departure sits in the 8am–11am window. Across every US flight scheduled in that window the on-time rate is 84.1%, and DL 665 runs level with that at 85.4%. Early departures usually start with an aircraft that has not flown yet that day, which is most of why the window does well.

Against the route

DL 665 next to ATL to ONT

Every carrier on ATL to ONT combined arrived on time 76.6% of the time across 937 flights, so DL 665 is 9 points ahead of it. Across its whole network Delta Air Lines managed 81.6%, which this flight beats by 4 points.

DL 665 against its route and carrier
Compared with	Flights	On time	Avg delay	Cancelled	Grade
DL 665	365	85.4%	54 min	2.47%	A
All Delta Air Lines on ATL–ONT	937	76.6%	55 min	1.71%	B
All carriers on ATL–ONT	937	76.6%	55 min	1.71%	B
Delta Air Lines, whole network	1,038,570	81.6%	71 min	1.62%	B

Across the year

DL 665 quarter by quarter

DL 665 did not run the same all year. Its best quarter was Jul–Sep 2025 at 92.4% on time and its weakest Apr–Jun 2026 at 77.5%, a swing of 15 points on roughly 91 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 flights92.4%
Oct–Dec 202592 flights87.6%
Jan–Mar 202690 flights83.7%
Apr–Jun 202691 flights77.5%

Scale runs 70% to 100%. Rows with fewer than 30 flights show a dash.

By weekday, DL 665 ranged from 82.4% on Friday to 90.2% 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.

Delay causes

Why DL 665 runs late

One category carries most of the weight here. Carrier accounts for 59% of the 2,803 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
59%
National Airspace System
26%
Late-arriving aircraft
13%
Extreme weather
2%

The largest share of delay minutes, 59%, 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 1,643 of the 2,803 delay minutes reported here. The split is drawn from 2,803 delay minutes reported on DL 665.

Cancellations sit at 2.47% against a national 1.81%, 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 8.1%. 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 roughly 55 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, 85.9% 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	85.9%	67 min	1.64%	A

What to do with this

Booking DL 665

For a booking, read DL 665 as 85.4% 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, July 2025 to June 2026. Last updated 15 September 2026; recomputed monthly. How this data is collected.

Key figures