Flight number record
DL 324
Delta Air Lines · Boston to Seattle
- Route
- BOS → SEA
- Departs
- 18:45
- Flights
- 363
- Period
- September 2025 to August 2026
Historical statistics for September 2025 to August 2026, not live status. For today’s DL 324, check with Delta Air Lines.
DL 324 draws a D. About one flight in three arrives at least 15 minutes late, and the typical late arrival is about an hour behind schedule. Build slack into anything you connect to. That rests on 363 flights, with a median arrival 4 minutes late.
The national on-time rate over the same period is 77.3%, so DL 324 runs 13 points behind the country as a whole. Across a thousand flights that is about 125 extra late arrivals.
Key figures
On time
64.8%
Arrivals under 15 minutes late, of 355 completed flights
Avg delay
62 min
Across delayed arrivals only, not all flights
Cancelled
2.20%
National rate is 1.89%
1 hour+ late
10.1%
National rate is 8.3%
These figures cover 363 flights between September 2025 and August 2026. Beyond the headline rate, 10.1% of arrivals land a full hour or more behind schedule, against 8.3% nationally.
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Schedule
When DL 324 flies
DL 324 flies BOS to SEA without a single fixed slot. Its most common scheduled departure was 18:45, used on 109 of 363 flights, with 18:55 (47 flights) next.
- Departs 18:45109 flights30.0%
- Departs 18:5547 flights12.9%
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 18:45 departure sits in the 5pm–8pm window. Across every US flight scheduled in that window the on-time rate is 68.0%, and DL 324 runs 3 points worse at 64.8%. By that time of day most aircraft have flown several legs already, and whatever went wrong earlier is still in the schedule.
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Against the route
DL 324 next to BOS to SEA
Every carrier on BOS to SEA combined arrived on time 70.1% of the time across 2,555 flights, so DL 324 is 5 points behind it. Delta flew 1,068 flights on the same city pair under all its flight numbers, including this one, and those ran 71.1% on time. Across its whole network Delta Air Lines managed 81.1%, which this flight trails by 16 points.
| Compared with | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| DL 324thin sample | 363 | 64.8% | 62 min | 2.20% | D |
| All Delta Air Lines on BOS–SEA | 1,068 | 71.1% | 57 min | 1.59% | C |
| All carriers on BOS–SEA | 2,555 | 70.1% | 55 min | 1.49% | C |
| Delta Air Lines, whole network | 1,039,517 | 81.1% | 71 min | 1.74% | B |
Across the year
DL 324 quarter by quarter
DL 324 did not run the same all year. Its best quarter was Jul–Sep 2025 at 73.3% on time and its weakest Oct–Dec 2025 at 55.1%, a swing of 18 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 flights73.3%
- Oct–Dec 202590 flights55.1%
- Jan–Mar 202690 flights58.6%
- Apr–Jun 202691 flights71.9%
- Jul–Sep 202662 flights73.3%
Scale runs 45% to 80%.
By weekday, DL 324 did best on Saturday at 74.5% on time and worst on Sunday at 53.1%. Each day rests on about 52 flights, so a gap of 21 points is worth noticing but could still narrow in another year.
Arrival by arrival
How late DL 324 runs when it is late
The 125 late arrivals split 46 under half an hour, 43 between 30 and 60 minutes, and 36 an hour or more.
- 15+ min early85 flights23.9%
- Within 15 min145 flights40.8%
- 15–29 min late46 flights13.0%
- 30–59 min late43 flights12.1%
- 1–2 hours late22 flights6.2%
- 2+ hours late14 flights3.9%
Scale runs 0% to 100%.
Share of 355 completed flights by arrival against schedule.
30 of 106 late departures made up the time and arrived on time, 28% of them. In the other direction, 49 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 SEA.
The worst days
Worst days for DL 324
The latest arrival of the period was on 24 February 2026, 13 hours 54 minutes behind schedule; most of its delay minutes were filed as carrier-caused (crew, maintenance, fuelling, baggage). The same cause led on three of the five worst days.
| Date | Arrived late by | Largest filed cause |
|---|---|---|
| 24 February 2026 | 13 hours 54 minutes | Carrier |
| 28 June 2026 | 4 hours 17 minutes | Carrier |
| 25 September 2025 | 3 hours 34 minutes | Late-arriving aircraft |
| 18 June 2026 | 3 hours 30 minutes | Late-arriving aircraft |
| 29 April 2026 | 3 hours 27 minutes | Carrier |
Delay causes
Why DL 324 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 7,782 reported delay minutes.
- 38%Late-arriving aircraft
- 30%Carrier
- 29%National Airspace System
- 4%Extreme weather
38% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 7,782 reported delay minutes here, that single category outweighs weather by 11 to one. The split is drawn from 7,782 delay minutes reported on DL 324.
Cancellations sit at 2.20% against a national 1.89%, which is ordinary. Diversions add another 0.00%.
Connections and routes
What a delay on this flight costs
10.1% of arrivals land a full hour or more behind schedule, against 8.3% nationally. Ninety minutes is the honest minimum for a connection here, and two hours if the onward flight is on a separate ticket.
At 2,496 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 363 flights under DL 324 in the data flew BOS to SEA. 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. 363 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 324
For a booking, DL 324 is one of the weaker ways to fly BOS to SEA: 5 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.
Related
Where to go next
- BOS to SEA, every carrier and departure
- SEA to BOS, the return direction
- Delta Air Lines 384 on the same route74.3%
- Alaska Airlines 459 on the same route72.3%
- Boston Logan International (BOS) delay statistics
- Seattle-Tacoma International (SEA) 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
- Why the first flight of the morning is statistically safest
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.