Flight number record

DL 571

Delta Air Lines · Boston to San Diego

Route: BOS → SAN
Departs: 17:35
Flights: 364
Period: July 2025 to June 2026

Historical statistics for July 2025 to June 2026, not live status. For today’s DL 571, check with Delta Air Lines.

DL 571 draws a C. About one flight in three arrives at least 15 minutes late, and the typical late arrival is roughly 45 minutes behind schedule. Build slack into anything you connect to. That rests on 364 flights, with a median arrival 1 minute late.

The national on-time rate over the same period is 77.6%, so DL 571 runs 10 points behind the country as a whole. Across a thousand flights that is about 97 extra late arrivals.

On time

67.9%

Arrivals under 15 minutes late, of 352 completed flights

Avg delay

43 min

Across delayed arrivals only, not all flights

Cancelled

1.65%

National rate is 1.81%

1 hour+ late

6.8%

National rate is 8.1%

These figures cover 364 flights between July 2025 and June 2026. On-time means an arrival less than 15 minutes after the scheduled gate time, the same threshold the Department of Transportation uses in its own reports. Cancelled and diverted flights are excluded from the on-time rate and counted separately, which is why the cancellation column matters on its own.

Schedule

When DL 571 flies

DL 571 flies BOS to SAN without a single fixed slot. Its most common scheduled departure was 17:35, used on 87 of 364 flights, with 17:25 (74 flights) and 17:10 (68 flights) next. Carriers retime flights through the season, so the rates here blend slightly different positions in the aircraft's day.

Departs 17:3587 flights23.9%
Departs 17:2574 flights20.3%
Departs 17:1068 flights18.7%

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 17:35 departure sits in the 5pm–8pm window. Across every US flight scheduled in that window the on-time rate is 68.2%, and DL 571 runs level with that at 67.9%. 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 571 next to BOS to SAN

Every carrier on BOS to SAN combined arrived on time 76.5% of the time across 1,818 flights, so DL 571 is 9 points behind it. Across its whole network Delta Air Lines managed 81.6%, which this flight trails by 14 points.

DL 571 against its route and carrier
Compared with	Flights	On time	Avg delay	Cancelled	Grade
DL 571thin sample	364	67.9%	43 min	1.65%	C
All Delta Air Lines on BOS–SANthin sample	364	67.9%	43 min	1.65%	C
All carriers on BOS–SAN	1,818	76.5%	56 min	1.38%	B
Delta Air Lines, whole network	1,038,570	81.6%	71 min	1.62%	B

Across the year

DL 571 quarter by quarter

Quarter by quarter DL 571 held fairly steady: 66.7% in Jul–Sep 2025, 66.7% in Oct–Dec 2025, 72.6% in Jan–Mar 2026 and 65.9% 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 flights66.7%
Oct–Dec 202591 flights66.7%
Jan–Mar 202690 flights72.6%
Apr–Jun 202691 flights65.9%

Scale runs 55% to 80%. Rows with fewer than 30 flights show a dash.

By weekday, DL 571 did best on Thursday at 75.5% on time and worst on Friday at 59.6%. 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 571 runs late

Carriers report a reason for every delay minute they cause, in five DOT categories. The split below is by minutes, not by number of flights, so a handful of very long weather delays weighs as much as many short ones. It covers 4,798 reported delay minutes.

National Airspace System
42%
Late-arriving aircraft
32%
Carrier
26%
Extreme weather
0%

42% of delay minutes are charged to the National Airspace System: air traffic volume, runway configuration, ground stops. No carrier can price its way out of that, which is why airport choice moves the number here more than carrier choice does. That is 2,004 minutes out of 4,798, against a national NAS share of 21%. The split is drawn from 4,798 delay minutes reported on DL 571.

Cancellations sit at 1.65% against a national 1.81%, which is ordinary. Diversions add another 1.65%.

Connections and routes

What a delay on this flight costs

6.8% 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 45 minutes, which a normal layover absorbs.

At 2,588 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.

The same number turns up on one other city pair in the data, including SAN to BOS (162), but none flew often enough under DL 571 to report a rate for. Carriers move flight numbers between routes, so the figures on this page apply to BOS to SAN only.

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 571

For a booking, DL 571 is one of the weaker ways to fly BOS to SAN: 9 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