Flight number record
DL 521
Delta Air Lines · Los Angeles to Dallas-Fort Worth
- Route
- LAX → DFW
- Departs
- 07:35
- Flights
- 353
- Period
- September 2025 to August 2026
Historical statistics for September 2025 to August 2026, not live status. For today’s DL 521, check with Delta Air Lines.
DL 521 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 a little over an hour. That rests on 353 flights, with a median arrival 8 minutes early.
Set against the rest of the country, DL 521's record is 12 points better than the US average of 77.3%. That gap is worth roughly 120 fewer late arrivals for every thousand flights.
Key figures
On time
89.3%
Arrivals under 15 minutes late, of 346 completed flights
Avg delay
81 min
Across delayed arrivals only, not all flights
Cancelled
1.70%
National rate is 1.89%
1 hour+ late
3.5%
National rate is 8.3%
These figures cover 353 flights between September 2025 and August 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.
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Schedule
When DL 521 flies
DL 521 flies LAX to DFW without a single fixed slot. Its most common scheduled departure was 07:35, used on 58 of 353 flights, with 08:50 (49 flights) and 09:50 (38 flights) next.
- Departs 07:3558 flights16.4%
- Departs 08:5049 flights13.9%
- Departs 09:5038 flights10.8%
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 07:35 departure sits in the 5am–8am window. Across every US flight scheduled in that window the on-time rate is 89.3%, and DL 521 runs level with that at 89.3%. 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 521 next to LAX to DFW
Every carrier on LAX to DFW combined arrived on time 74.9% of the time across 6,178 flights, so DL 521 is 14 points ahead of it. Delta flew 757 flights on the same city pair under all its flight numbers, including this one, and those ran 85.4% on time. Across its whole network Delta Air Lines managed 81.1%, which this flight beats by 8 points.
| Compared with | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| DL 521thin sample | 353 | 89.3% | 81 min | 1.70% | A |
| All Delta Air Lines on LAX–DFW | 757 | 85.4% | 75 min | 1.45% | A |
| All carriers on LAX–DFW | 6,178 | 74.9% | 79 min | 2.22% | C |
| Delta Air Lines, whole network | 1,039,517 | 81.1% | 71 min | 1.74% | B |
Across the year
DL 521 quarter by quarter
Quarter by quarter DL 521 held fairly steady: 90.0% in Jul–Sep 2025, 88.8% in Oct–Dec 2025, 86.7% in Jan–Mar 2026, 88.4% in Apr–Jun 2026 and 94.8% in Jul–Sep 2026. A spread of 8 points is about what a sample of this size moves on its own, so the annual figure is a fair summary.
- Jul–Sep 202530 flights90.0%
- Oct–Dec 202592 flights88.8%
- Jan–Mar 202685 flights86.7%
- Apr–Jun 202688 flights88.4%
- Jul–Sep 202658 flights94.8%
Scale runs 80% to 100%.
By weekday, DL 521 did best on Friday at 94.0% on time and worst on Thursday at 82.0%. Each day rests on about 50 flights, so a gap of 12 points is worth noticing but could still narrow in another year.
Arrival by arrival
How late DL 521 runs when it is late
DL 521 often beats the schedule: 87 of 346 completed flights, 25%, arrived 15 minutes or more early. The 37 late arrivals split 14 under half an hour, 11 between 30 and 60 minutes, and 12 an hour or more.
- 15+ min early87 flights25.1%
- Within 15 min222 flights64.2%
- 15–29 min late14 flights4.0%
- 30–59 min late11 flights3.2%
- 1–2 hours late6 flights1.7%
- 2+ hours late6 flights1.7%
Scale runs 0% to 100%.
Share of 346 completed flights by arrival against schedule.
5 of 33 late departures made up the time and arrived on time, 15% of them. 9 flights left on time and still arrived late.
The worst days
Worst days for DL 521
The latest arrival of the period was on 25 June 2026, 8 hours behind schedule; most of its delay minutes were filed as carrier-caused (crew, maintenance, fuelling, baggage). Three of the five worst days fell in June 2026.
| Date | Arrived late by | Largest filed cause |
|---|---|---|
| 25 June 2026 | 8 hours | Carrier |
| 9 June 2026 | 7 hours 20 minutes | Carrier |
| 11 June 2026 | 5 hours 21 minutes | Carrier |
| 26 January 2026 | 3 hours 45 minutes | National Airspace System |
| 24 November 2025 | 3 hours 2 minutes | Late-arriving aircraft |
Delay causes
Why DL 521 runs late
Carrier accounts for 61% of the 2,998 delay minutes carriers reported here, and the remaining four split what is left.
- 61%Carrier
- 21%Late-arriving aircraft
- 18%National Airspace System
The largest share of delay minutes, 61%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. It accounts for 1,832 of the 2,998 delay minutes reported here. The split is drawn from 2,998 delay minutes reported on DL 521.
Cancellations sit at 1.70% against a national 1.89%, which is ordinary. Diversions add another 0.28%.
Connections and routes
What a delay on this flight costs
Badly late arrivals are rare here: only 3.5% 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.
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.
The same number turns up on one other city pair in the data, including DFW to LAX (87), 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. 353 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 89.3% on time with 1.70% cancelled over 353 flights. Those are rates from the past twelve months, not a forecast for any particular day.
Related
Where to go next
- LAX to DFW, every carrier and departure
- DFW to LAX, the return direction
- Delta Air Lines 420 on the same route81.2%
- American Airlines 2746 on the same route87.0%
- Los Angeles International (LAX) delay statistics
- Dallas/Fort Worth International (DFW) delay statistics
- Delta Air Lines on-time record
- Every Delta Air Lines flight number with a record
- The most and least reliable flight numbers in the US
- Worst months to fly in the US, ranked by the data
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 ; recomputed monthly. How this data is collected.