Carrier route record

DLBOS→DTW

Delta Air Lines · Boston to Detroit

Flights: 1,712
Period: July 2025 to June 2026
Share of route: 66%
Carriers: 4

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

Delta on BOS to DTW lands a B, 2 points better than the national rate of 77.6%. About one flight in five arrives 15 minutes late or worse, and those flights are late by a little over an hour on average. That is a workable record, not a spotless one. That rests on 1,712 flights, with a median arrival 9 minutes early.

The US average over the same twelve months is 77.6%, so there is little to separate Delta on BOS to DTW from the country as a whole. The variation that matters here is internal: which carrier, and what time of day.

On time

79.6%

Arrivals under 15 minutes late, of 1,674 completed flights

Avg delay

77 min

Across delayed arrivals only, not all flights

Cancelled

2.04%

National rate is 1.81%

Whole route

77.6%

Every carrier on BOS to DTW, 2,591 flights

These figures cover 1,712 flights between July 2025 and June 2026. Beyond the headline rate, 8.2% 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.

Carrier by carrier

Delta against every carrier on BOS to DTW

Delta flew 1,712 of the 2,591 flights on BOS to DTW, most of the route. Its 79.6% on time is 2 points better than the route as a whole, which runs 77.6%. Ranked by on-time rate it is number three of four carriers on the route, where the range runs from Republic at 100.0% to JetBlue at 71.7%. Two of those carriers flew fewer than 365 flights here, so treat their positions as rough.

Only one carrier clears this site's 365-flight floor here, so there is no comparison to draw. The table below is the full picture.

On-time performance by carrier on BOS to DTW
Airline	Flights	On time	Avg delay	Cancelled	Grade
Republic Airwaysthin sample	1	100.0%	—	0.00%	A+
Spirit Airlinesthin sample	155	82.6%	62 min	0.00%	B+
Delta Air Lines (this page)	1,712	79.6%	77 min	2.04%	B
JetBlue Airways	723	71.7%	72 min	2.77%	C

Flight by flight

Delta flight numbers on BOS to DTW

Departure window

When Delta runs best on this route

Departure time matters more here than the choice of carrier. The gap between the best and worst window is 37 points, against half a point between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.

5am–8am366 flights94.7%
8am–11am365 flights89.7%
11am–2pm364 flights79.8%
2pm–5pm78 flights70.5%
5pm–8pm284 flights69.1%
8pm–5am255 flights57.3%

Scale runs 50% to 100%. Rows with fewer than 30 flights show a dash.

The 8pm–5am window is where this operation falls apart: 57.3% on time, against 94.7% for the 5am–8am slot. By evening the aircraft flying these rotations have absorbed a full day of small delays and there is no slack left to recover in. The 5am–8am window is the busiest, with 366 flights scheduled in it.

Across the year

Delta on BOS to DTW through the year

Darker means more delays. Figures are on-time percentages.August best, December worst

December is the weak month at 66.2% on time, against 88.0% in August. Winter delays cluster: a single storm system can account for most of a month's shortfall, so an average December hides both very good weeks and genuinely unflyable days. March was the busiest month here, with 150 flights.

Across the week, Saturday is the strongest day at 84.0% on time and Sunday the weakest at 75.6%. 8 points is a smaller lever than departure hour, but it is free.

Delay causes

Why Delta runs late on this route

One category carries most of the weight here. Late-arriving aircraft accounts for 47% of the 26,000 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.

Late-arriving aircraft
47%
Carrier
36%
National Airspace System
15%
Extreme weather
2%

47% 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 26,000 reported delay minutes here, that single category outweighs weather by 24 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 26,388 reported delay minutes.

The largest share of delay minutes, 36%, 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 9,457 of the 26,000 delay minutes reported here.

Cancellations sit at 2.04% against a national 1.81%, which is ordinary. Diversions add another 0.18%.

Connections and stage length

What a delay here costs

8.2% of arrivals land an hour or more late, close to the national 8.1%. That is the figure that decides a connection, and it says a 60 to 75 minute layover is reasonable here while anything under 45 minutes is a bet. Most delays on this route last a little over an hour, which a normal layover absorbs.

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.

The return leg is a different operation and performs like one: it runs 74.9% on time across 1,710 flights, 5 points below this direction. Departure banks, aircraft rotations and the congestion at each end all differ, so scoring the two directions together would average away a real 5 points of difference.

The sample behind these figures is 1,712 flights, enough that the headline rate is stable to within roughly a point. The hour-block and month splits divide that further, so read the thinner bars with more caution than the headline.

What to do with this

Booking Delta on BOS to DTW

Put together: the calendar is the biggest lever here, not the carrier or the hour. August runs 88.0% on time and December 66.2%, a swing of 22 points. If the dates move at all, move them out of December before you think about anything else. 1,674 completed flights over 12 months sit behind that.

Where to go next

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