Flight number record
DL 506
Delta Air Lines · Seattle to Miami
- Route
- SEA → MIA
- Departs
- 08:00
- Flights
- 365
- Period
- September 2025 to August 2026
Historical statistics for September 2025 to August 2026, not live status. For today’s DL 506, check with Delta Air Lines.
DL 506 lands a B, 3 points better than the national rate of 77.3%. About one flight in five arrives 15 minutes late or worse, and those flights are late by about an hour on average. That rests on 365 flights, with a median arrival 8 minutes early.
Key figures
On time
80.7%
Arrivals under 15 minutes late, of 357 completed flights
Avg delay
65 min
Across delayed arrivals only, not all flights
Cancelled
1.37%
National rate is 1.89%
1 hour+ late
5.6%
National rate is 8.3%
These figures cover 365 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 506 flies
DL 506 flies SEA to MIA without a single fixed slot. Its most common scheduled departure was 08:00, used on 70 of 365 flights, with 07:55 (41 flights) and 07:35 (37 flights) next.
- Departs 08:0070 flights19.2%
- Departs 07:5541 flights11.2%
- Departs 07:3537 flights10.1%
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 506 runs 3 points worse at 80.7%. 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 506 next to SEA to MIA
Every carrier on SEA to MIA combined arrived on time 79.7% of the time across 1,231 flights, so DL 506 is about level with it. Across its whole network Delta Air Lines managed 81.1%, close to this flight's figure.
| Compared with | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| DL 506 | 365 | 80.7% | 65 min | 1.37% | B |
| All Delta Air Lines on SEA–MIA | 365 | 80.7% | 65 min | 1.37% | B |
| All carriers on SEA–MIA | 1,231 | 79.7% | 59 min | 0.81% | B+ |
| Delta Air Lines, whole network | 1,039,517 | 81.1% | 71 min | 1.74% | B |
Across the year
DL 506 quarter by quarter
DL 506 did not run the same all year. Its best quarter was Oct–Dec 2025 at 85.4% on time and its weakest Jan–Mar 2026 at 73.9%, a swing of 12 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 202530 flights—
- Oct–Dec 202592 flights85.4%
- Jan–Mar 202690 flights73.9%
- Apr–Jun 202691 flights84.6%
- Jul–Sep 202662 flights83.3%
Scale runs 65% to 90%. Rows with fewer than 30 flights show a dash.
By weekday, DL 506 ranged from 74.5% on Monday to 84.3% on Wednesday. With about 52 flights behind each day, a spread of 10 points is inside normal variation, so the day you fly is not worth changing for this flight.
Arrival by arrival
How late DL 506 runs when it is late
DL 506 often beats the schedule: 130 of 357 completed flights, 36%, arrived 15 minutes or more early. The 69 late arrivals split 23 under half an hour, 26 between 30 and 60 minutes, and 20 an hour or more.
- 15+ min early130 flights36.4%
- Within 15 min158 flights44.3%
- 15–29 min late23 flights6.4%
- 30–59 min late26 flights7.3%
- 1–2 hours late9 flights2.5%
- 2+ hours late11 flights3.1%
Scale runs 0% to 100%.
Share of 357 completed flights by arrival against schedule.
6 of 36 late departures made up the time and arrived on time, 17% of them. In the other direction, 39 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 MIA.
The worst days
Worst days for DL 506
The latest arrival of the period was on 5 June 2026, 5 hours 56 minutes behind schedule; most of its delay minutes were filed as carrier-caused (crew, maintenance, fuelling, baggage). The same cause led on five of the five worst days.
| Date | Arrived late by | Largest filed cause |
|---|---|---|
| 5 June 2026 | 5 hours 56 minutes | Carrier |
| 1 June 2026 | 4 hours 17 minutes | Carrier |
| 12 February 2026 | 4 hours 16 minutes | Carrier |
| 30 August 2026 | 3 hours 59 minutes | Carrier |
| 15 May 2026 | 3 hours 22 minutes | Carrier |
Delay causes
Why DL 506 runs late
Carrier accounts for 58% of the 4,511 delay minutes carriers reported here, and the remaining four split what is left.
- 58%Carrier
- 38%National Airspace System
- 3%Extreme weather
- 0%Late-arriving aircraft
The largest share of delay minutes, 58%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. It accounts for 2,633 of the 4,511 delay minutes reported here. The split is drawn from 4,511 delay minutes reported on DL 506.
Cancellations sit at 1.37% against a national 1.89%, which is ordinary. Diversions add another 0.82%.
Connections and routes
What a delay on this flight costs
5.6% of arrivals land an hour or more late, close to the national 8.3%, so a 60 to 75 minute layover is reasonable here while anything under 45 minutes is a bet. Most delays on this route last about an hour, which a normal layover absorbs.
At 2,724 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 506 is not only a SEA to MIA flight. It also flew MIA to SEA (257 flights, 61.2% 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.
| Also flown as | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| MIA to SEAthin sample | 257 | 61.2% | 95 min | 2.33% | D |
What to do with this
Booking DL 506
For a booking, read DL 506 as 80.7% on time with 1.37% cancelled over 365 flights. Those are rates from the past twelve months, not a forecast for any particular day.
Related
Where to go next
- SEA to MIA, every carrier and departure
- MIA to SEA, the return direction
- Alaska Airlines 305 on the same route79.1%
- Seattle-Tacoma International (SEA) delay statistics
- Miami International (MIA) 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.