Flight number record
DL 324
Delta Air Lines · Boston to Seattle
- Route
- BOS → SEA
- Departs
- 18:45
- Flights
- 363
- Period
- July 2025 to June 2026
Historical statistics for July 2025 to June 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 77.6%, so DL 324 runs 13 points behind the country as a whole. Across a thousand flights that is about 131 extra late arrivals.
Key figures
On time
64.5%
Arrivals under 15 minutes late, of 355 completed flights
Avg delay
64 min
Across delayed arrivals only, not all flights
Cancelled
2.20%
National rate is 1.81%
1 hour+ late
10.1%
National rate is 8.1%
These figures cover 363 flights between July 2025 and June 2026. Beyond the headline rate, 10.1% of arrivals land a full hour or more behind schedule. That is the number that wrecks a connection, and it is not visible in an on-time percentage alone.
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 104 of 363 flights, with 18:55 (52 flights) and 18:50 (45 flights) next. Carriers retime flights through the season, so the rates here blend slightly different positions in the aircraft's day.
- Departs 18:45104 flights28.7%
- Departs 18:5552 flights14.3%
- Departs 18:5045 flights12.4%
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 18:45 departure sits in the 5pm–8pm window. Across every US flight scheduled in that window the on-time rate is 68.2%, and DL 324 runs 4 points worse at 64.5%. 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 324 next to BOS to SEA
Every carrier on BOS to SEA combined arrived on time 71.4% of the time across 2,461 flights, so DL 324 is 7 points behind it. Delta flew 1,006 flights on the same city pair under all its flight numbers, including this one, and those ran 71.6% on time. Across its whole network Delta Air Lines managed 81.6%, which this flight trails by 17 points.
| Compared with | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| DL 324thin sample | 363 | 64.5% | 64 min | 2.20% | D |
| All Delta Air Lines on BOS–SEA | 1,006 | 71.6% | 55 min | 1.59% | C |
| All carriers on BOS–SEA | 2,461 | 71.4% | 54 min | 1.26% | C |
| Delta Air Lines, whole network | 1,038,570 | 81.6% | 71 min | 1.62% | 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 72.2% on time and its weakest Oct–Dec 2025 at 55.1%, a swing of 17 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 202592 flights72.2%
- Oct–Dec 202590 flights55.1%
- Jan–Mar 202690 flights58.6%
- Apr–Jun 202691 flights71.9%
Scale runs 45% to 80%. Rows with fewer than 30 flights show a dash.
By weekday, DL 324 did best on Friday at 70.0% on time and worst on Sunday at 56.2%. Each day rests on about 52 flights, so a gap of 14 points is worth noticing but could still narrow in another year.
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 8,096 reported delay minutes.
- 36%Late-arriving aircraft
- 32%Carrier
- 28%National Airspace System
- 3%Extreme weather
36% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. That is a cascade, and cascades start small and grow through the day. Across 8,096 reported delay minutes here, that single category outweighs weather by 10 to one. It is the strongest argument for booking the first departure of the morning, when the aircraft has been sitting at the gate overnight with nothing to inherit. The split is drawn from 8,096 delay minutes reported on DL 324.
Cancellations sit at 2.20% against a national 1.81%, which is ordinary. Diversions add another 0.00%.
Connections and routes
What a delay on this flight costs
For anyone connecting, the number to weigh is not the on-time rate but the tail behind it. 10.1% of arrivals land a full hour or more behind schedule, against 8.1% nationally. A 45-minute layover does not survive that, and no amount of walking quickly changes it. Ninety minutes is the honest minimum 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: 7 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 route75.1%
- Alaska Airlines 459 on the same route72.1%
- 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, July 2025 to June 2026. Last updated 15 September 2026; recomputed monthly. How this data is collected.