Flight number record

DL 521

Delta Air Lines · Los Angeles to Dallas-Fort Worth

Route: LAX → DFW
Departs: 08:35
Flights: 357
Period: July 2025 to June 2026

Historical statistics for July 2025 to June 2026, not live status. For today’s DL 521, check with Delta Air Lines.

DL 521 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 9 points better than the national rate of 77.6%. When something does go wrong the average delay runs an hour and a half. That rests on 357 flights, with a median arrival 8 minutes early.

Set against the rest of the country, DL 521's record is 9 points better than the US average of 77.6%. That gap is worth roughly 92 fewer late arrivals for every thousand flights.

On time

86.8%

Arrivals under 15 minutes late, of 348 completed flights

Avg delay

84 min

Across delayed arrivals only, not all flights

Cancelled

1.96%

National rate is 1.81%

1 hour+ late

4.0%

National rate is 8.1%

These figures cover 357 flights between July 2025 and June 2026. The median arrival is 8 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 521 flies

DL 521 flies LAX to DFW without a single fixed slot. Its most common scheduled departure was 08:35, used on 62 of 357 flights, with 08:50 (49 flights) and 09:50 (38 flights) next. Carriers retime flights through the season, so the rates here blend slightly different positions in the aircraft's day.

Departs 08:3562 flights17.4%
Departs 08:5049 flights13.7%
Departs 09:5038 flights10.6%

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 08:35 departure sits in the 8am–11am window. Across every US flight scheduled in that window the on-time rate is 84.1%, and DL 521 runs 3 points better at 86.8%. 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 521 next to LAX to DFW

Every carrier on LAX to DFW combined arrived on time 74.2% of the time across 6,231 flights, so DL 521 is 13 points ahead of it. Delta flew 718 flights on the same city pair under all its flight numbers, including this one, and those ran 83.6% on time. Across its whole network Delta Air Lines managed 81.6%, which this flight beats by 5 points.

DL 521 against its route and carrier
Compared with	Flights	On time	Avg delay	Cancelled	Grade
DL 521thin sample	357	86.8%	84 min	1.96%	A
All Delta Air Lines on LAX–DFW	718	83.6%	80 min	1.81%	B
All carriers on LAX–DFW	6,231	74.2%	90 min	2.44%	C
Delta Air Lines, whole network	1,038,570	81.6%	71 min	1.62%	B

Across the year

DL 521 quarter by quarter

Quarter by quarter DL 521 held fairly steady: 83.3% in Jul–Sep 2025, 88.8% in Oct–Dec 2025, 86.7% in Jan–Mar 2026 and 88.4% in Apr–Jun 2026. A spread of 6 points is about what a sample of this size moves on its own, so the annual figure is a fair summary.

Jul–Sep 202592 flights83.3%
Oct–Dec 202592 flights88.8%
Jan–Mar 202685 flights86.7%
Apr–Jun 202688 flights88.4%

Scale runs 75% to 95%. Rows with fewer than 30 flights show a dash.

By weekday, DL 521 did best on Tuesday at 92.2% on time and worst on Saturday at 76.1%. Each day rests on about 51 flights, so a gap of 16 points is worth noticing but could still narrow in another year.

Delay causes

Why DL 521 runs late

One category carries most of the weight here. Carrier accounts for 53% of the 3,842 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
53%
National Airspace System
30%
Late-arriving aircraft
17%

The largest share of delay minutes, 53%, 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 2,026 of the 3,842 delay minutes reported here. The split is drawn from 3,842 delay minutes reported on DL 521.

Cancellations sit at 1.96% against a national 1.81%, which is ordinary. Diversions add another 0.56%.

Connections and routes

What a delay on this flight costs

Badly late arrivals are rare here: only 4.0% land an hour or more behind schedule, against 8.1% 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.

The 1,235 miles between these two airports put this in the middle of the US network, around two and a half to three hours of block time. That is enough cruise to absorb a ten-minute late pushback and not enough to absorb thirty. It is also long enough that the aircraft usually flies three or four legs a day rather than six, which slows how fast delay compounds.

The same number turns up on one other city pair in the data, including DFW to LAX (39), but none flew often enough under DL 521 to report a rate for. Carriers move flight numbers between routes, so the figures on this page apply to LAX to DFW only.

One caution: this is a thin sample. 357 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 521

For a booking, read DL 521 as 86.8% on time with 1.96% cancelled over 357 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