Flight number record

DL 384

Delta Air Lines · Boston to Seattle

Route: BOS → SEA
Departs: 07:15
Flights: 365
Period: July 2025 to June 2026

Historical statistics for July 2025 to June 2026, not live status. For today’s DL 384, check with Delta Air Lines.

DL 384 sits in the middle of the pack with a B. Close to three flights in four arrive on time by the DOT's definition, 3 points worse than the national rate of 77.6%. The late ones land about 40 minutes behind schedule. That rests on 365 flights, with a median arrival 2 minutes late.

On time

75.1%

Arrivals under 15 minutes late, of 357 completed flights

Avg delay

40 min

Across delayed arrivals only, not all flights

Cancelled

1.92%

National rate is 1.81%

1 hour+ late

3.4%

National rate is 8.1%

These figures cover 365 flights between July 2025 and June 2026. On-time means an arrival less than 15 minutes after the scheduled gate time, the same threshold the Department of Transportation uses in its own reports. Cancelled and diverted flights are excluded from the on-time rate and counted separately, which is why the cancellation column matters on its own.

Schedule

When DL 384 flies

DL 384 flies BOS to SEA without a single fixed slot. Its most common scheduled departure was 07:15, used on 119 of 365 flights, with 07:25 (97 flights) next. Carriers retime flights through the season, so the rates here blend slightly different positions in the aircraft's day.

Departs 07:15119 flights32.6%
Departs 07:2597 flights26.6%

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 07:15 departure sits in the 5am–8am window. Across every US flight scheduled in that window the on-time rate is 89.3%, and DL 384 runs 14 points worse at 75.1%. 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 384 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 384 is 4 points ahead of 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 7 points.

DL 384 against its route and carrier
Compared with	Flights	On time	Avg delay	Cancelled	Grade
DL 384	365	75.1%	40 min	1.92%	B
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 384 quarter by quarter

DL 384 did not run the same all year. Its best quarter was Jul–Sep 2025 at 87.8% on time and its weakest Jan–Mar 2026 at 57.0%, a swing of 31 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 flights87.8%
Oct–Dec 202592 flights74.7%
Jan–Mar 202690 flights57.0%
Apr–Jun 202691 flights80.0%

Scale runs 50% to 95%. Rows with fewer than 30 flights show a dash.

By weekday, DL 384 did best on Sunday at 80.8% on time and worst on Tuesday at 68.6%. Each day rests on about 52 flights, so a gap of 12 points is worth noticing but could still narrow in another year.

Delay causes

Why DL 384 runs late

One category carries most of the weight here. National Airspace System accounts for 50% of the 3,540 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.

National Airspace System
50%
Carrier
33%
Late-arriving aircraft
17%
Extreme weather
1%

50% of delay minutes are charged to the National Airspace System: air traffic volume, runway configuration, ground stops. No carrier can price its way out of that, which is why airport choice moves the number here more than carrier choice does. That is 1,766 minutes out of 3,540, against a national NAS share of 21%. The split is drawn from 3,540 delay minutes reported on DL 384.

Cancellations sit at 1.92% against a national 1.81%, which is ordinary. Diversions add another 0.27%.

Connections and routes

What a delay on this flight costs

Badly late arrivals are rare here: only 3.4% 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.

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 365 flights under DL 384 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. 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.

What to do with this

Booking DL 384

For a booking, read DL 384 as 75.1% on time with 1.92% cancelled over 365 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