Flight number record

DL 640

Delta Air Lines · San Francisco to Atlanta

Route: SFO → ATL
Departs: 08:00
Flights: 364
Period: September 2025 to August 2026

Historical statistics for September 2025 to August 2026, not live status. For today’s DL 640, check with Delta Air Lines.

DL 640 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 12 points better than the national rate of 77.3%. When something does go wrong the average delay runs about an hour. That rests on 364 flights, with a median arrival 11 minutes early.

Set against the rest of the country, DL 640's record is 12 points better than the US average of 77.3%. That gap is worth roughly 122 fewer late arrivals for every thousand flights.

On time

89.5%

Arrivals under 15 minutes late, of 362 completed flights

Avg delay

65 min

Across delayed arrivals only, not all flights

Cancelled

0.55%

National rate is 1.89%

1 hour+ late

2.8%

National rate is 8.3%

These figures cover 364 flights between September 2025 and August 2026. The median arrival is 11 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 640 flies

DL 640 flies SFO to ATL without a single fixed slot. Its most common scheduled departure was 08:00, used on 166 of 364 flights, with 07:15 (74 flights) and 07:50 (56 flights) next.

Departs 08:00166 flights45.6%
Departs 07:1574 flights20.3%
Departs 07:5056 flights15.4%

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 08:00 departure sits in the 8am–11am window. Across every US flight scheduled in that window the on-time rate is 83.9%, and DL 640 runs 6 points better at 89.5%. 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 640 next to SFO to ATL

Every carrier on SFO to ATL combined arrived on time 80.2% of the time across 3,337 flights, so DL 640 is 9 points ahead of it. Delta flew 2,390 flights on the same city pair under all its flight numbers, including this one, and those ran 81.1% on time. Across its whole network Delta Air Lines managed 81.1%, which this flight beats by 8 points.

DL 640 against its route and carrier
Compared with	Flights	On time	Avg delay	Cancelled	Grade
DL 640thin sample	364	89.5%	65 min	0.55%	A+
All Delta Air Lines on SFO–ATL	2,390	81.1%	70 min	0.71%	B+
All carriers on SFO–ATL	3,337	80.2%	68 min	0.87%	B+
Delta Air Lines, whole network	1,039,517	81.1%	71 min	1.74%	B

Across the year

DL 640 quarter by quarter

DL 640 did not run the same all year. Its best quarter was Jul–Sep 2025 at 96.7% on time and its weakest Jul–Sep 2026 at 80.6%, a swing of 16 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 flights96.7%
Oct–Dec 202591 flights95.6%
Jan–Mar 202690 flights94.4%
Apr–Jun 202691 flights82.4%
Jul–Sep 202662 flights80.6%

Scale runs 70% to 100%.

By weekday, DL 640 ranged from 82.4% on Saturday to 94.2% on Thursday. With about 52 flights behind each day, a spread of 12 points is inside normal variation, so the day you fly is not worth changing for this flight.

Arrival by arrival

How late DL 640 runs when it is late

DL 640 often beats the schedule: 143 of 362 completed flights, 40%, arrived 15 minutes or more early. The 38 late arrivals split 17 under half an hour, 11 between 30 and 60 minutes, and 10 an hour or more.

15+ min early143 flights39.5%
Within 15 min181 flights50.0%
15–29 min late17 flights4.7%
30–59 min late11 flights3.0%
1–2 hours late6 flights1.7%
2+ hours late4 flights1.1%

Scale runs 0% to 100%.

Share of 362 completed flights by arrival against schedule.

A late pushback is often recovered here: of 26 departures that left 15 minutes late or more, 8 still arrived on time. In the other direction, 20 flights left on time yet arrived 15 minutes late or more, so that delay built up after pushback: in the air, in a holding pattern or on the ground at ATL.

The worst days

Worst days for DL 640

The latest arrival of the period was on 10 May 2026, 6 hours 53 minutes behind schedule; most of its delay minutes were filed as carrier-caused (crew, maintenance, fuelling, baggage). The five worst days are spread across May, April, September, October and January, with no single month standing out.

The latest arrivals of DL 640 in the period
Date	Arrived late by	Largest filed cause
10 May 2026	6 hours 53 minutes	Carrier
29 April 2026	5 hours 29 minutes	Late-arriving aircraft
2 September 2025	4 hours 16 minutes	Carrier
20 October 2025	2 hours 26 minutes	Late-arriving aircraft
25 January 2026	1 hour 45 minutes	National Airspace System

Delay causes

Why DL 640 runs late

Carrier accounts for 51% of the 2,475 delay minutes carriers reported here, and the remaining four split what is left.

Carrier
51%
National Airspace System
32%
Late-arriving aircraft
17%

The largest share of delay minutes, 51%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. It accounts for 1,267 of the 2,475 delay minutes reported here. The split is drawn from 2,475 delay minutes reported on DL 640.

Cancellations are rare at 0.55%, 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

Badly late arrivals are rare here: only 2.8% land an hour or more behind schedule, against 8.3% 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 2,139 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 364 flights under DL 640 in the data flew SFO to ATL. 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. 364 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 640

For a booking, DL 640 has one of the better records a US domestic flight can show: 89.5% 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, September 2025 to August 2026. Last updated 22 October 2026; recomputed monthly. How this data is collected.

Key figures