Flight number record

DL 1187

Delta Air Lines · Detroit to Boston

Route: DTW → BOS
Departs: 21:50
Flights: 352
Period: July 2025 to June 2026

Historical statistics for July 2025 to June 2026, not live status. For today’s DL 1187, check with Delta Air Lines.

DL 1187 sits in the middle of the pack with a C. About seven flights in ten arrive on time by the DOT's definition, 6 points worse than the national rate of 77.6%. The late ones land a little over an hour behind schedule. That rests on 352 flights, with a median arrival 6 minutes early.

The national on-time rate over the same period is 77.6%, so DL 1187 runs 6 points behind the country as a whole. Across a thousand flights that is about 64 extra late arrivals.

On time

71.2%

Arrivals under 15 minutes late, of 344 completed flights

Avg delay

71 min

Across delayed arrivals only, not all flights

Cancelled

2.27%

National rate is 1.81%

1 hour+ late

11.0%

National rate is 8.1%

These figures cover 352 flights between July 2025 and June 2026. Beyond the headline rate, 11.0% 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 1187 flies

DL 1187 flies DTW to BOS without a single fixed slot. Its most common scheduled departure was 21:50, used on 134 of 352 flights, with 21:56 (60 flights) next. Carriers retime flights through the season, so the rates here blend slightly different positions in the aircraft's day.

Departs 21:50134 flights38.1%
Departs 21:5660 flights17.0%

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 21:50 departure sits in the 8pm–5am window. Across every US flight scheduled in that window the on-time rate is 70.5%, and DL 1187 runs level with that at 71.2%. 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 1187 next to DTW to BOS

Every carrier on DTW to BOS combined arrived on time 74.8% of the time across 2,588 flights, so DL 1187 is 4 points behind it. Delta flew 1,710 flights on the same city pair under all its flight numbers, including this one, and those ran 74.9% on time. Across its whole network Delta Air Lines managed 81.6%, which this flight trails by 10 points.

DL 1187 against its route and carrier
Compared with	Flights	On time	Avg delay	Cancelled	Grade
DL 1187thin sample	352	71.2%	71 min	2.27%	C
All Delta Air Lines on DTW–BOS	1,710	74.9%	67 min	1.81%	C
All carriers on DTW–BOS	2,588	74.8%	72 min	2.09%	C
Delta Air Lines, whole network	1,038,570	81.6%	71 min	1.62%	B

Across the year

DL 1187 quarter by quarter

DL 1187 did not run the same all year. Its best quarter was Jan–Mar 2026 at 75.6% on time and its weakest Jul–Sep 2025 at 62.0%, a swing of 14 points on roughly 88 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 202581 flights62.0%
Oct–Dec 202591 flights72.2%
Jan–Mar 202690 flights75.6%
Apr–Jun 202690 flights74.2%

Scale runs 55% to 80%. Rows with fewer than 30 flights show a dash.

By weekday, DL 1187 did best on Thursday at 78.0% on time and worst on Sunday at 56.2%. Each day rests on about 50 flights, so a gap of 22 points is worth noticing but could still narrow in another year.

Delay causes

Why DL 1187 runs late

One category carries most of the weight here. Carrier accounts for 45% of the 7,002 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.

Carrier
45%
Late-arriving aircraft
29%
National Airspace System
23%
Extreme weather
2%

The largest share of delay minutes, 45%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. Unlike weather, that is a management outcome, and it is the category where the gap between two carriers on the same schedule is genuinely earned. It accounts for 3,167 of the 7,002 delay minutes reported here. The split is drawn from 7,002 delay minutes reported on DL 1187.

Cancellations sit at 2.27% 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. 11.0% 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.

The 632 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. It is also long enough that the aircraft usually flies three or four legs a day rather than six, which slows how fast delay compounds.

Every one of the 352 flights under DL 1187 in the data flew DTW to BOS. 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. 352 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 1187

For a booking, read DL 1187 as 71.2% on time with 2.27% cancelled over 352 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