Carrier route record

NKDTW→BOS

Spirit Airlines · Detroit to Boston

Flights: 154
Period: July 2025 to June 2026
Share of route: 6%
Carriers: 4

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

Spirit on DTW to BOS lands a B+, level with the national rate of 77.6%. Roughly one flight in five arrives 15 minutes late or worse, and those flights are late by about an hour on average. That is a workable record, not a spotless one. That rests on 154 flights. The strongest carrier on the route with a full sample, Delta Air Lines, flew 1,710 at 74.9% on time.

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

On time

77.9%

Arrivals under 15 minutes late, of 154 completed flights

Avg delay

60 min

Across delayed arrivals only, not all flights

Cancelled

0.00%

National rate is 1.81%

Whole route

74.8%

Every carrier on DTW to BOS, 2,588 flights

These figures cover 154 flights between July 2025 and June 2026. Beyond the headline rate, 9.1% 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.

Carrier by carrier

Spirit against every carrier on DTW to BOS

Spirit flew 154 of the 2,588 flights on DTW to BOS, about 6% of it. Its 77.9% on time is 3 points better than the route as a whole, which runs 74.8%. Ranked by on-time rate it is first of four carriers on the route, where the range runs from Spirit at 77.9% to Republic at 0.0%. One of those carriers flew fewer than 365 flights here, so treat their positions as rough.

The two carriers here are closely matched: about a point separate the best from the worst. At that spread, schedule and price are better tie-breakers than reliability. Sample sizes are shown so you can see which rows are worth weighing.

On-time performance by carrier on DTW to BOS
Airline	Flights	On time	Avg delay	Cancelled	Grade
Spirit Airlines (this page)thin sample	154	77.9%	60 min	0.00%	B+
Delta Air Lines	1,710	74.9%	67 min	1.81%	C
JetBlue Airways	723	74.0%	87 min	3.18%	C−
Republic Airwaysthin sample	1	0.0%	20 min	0.00%	F+

JetBlue Airways cancels 3.2% of what it schedules here, the highest in the table. A cancelled flight never appears in an on-time rate, so read that column alongside the punctuality one rather than after it.

Departure window

When Spirit runs best on this route

Departure time is the single lever a traveller controls, and it moves the odds more than most people expect. Each bar below is the on-time rate for flights scheduled to leave inside that window, across 154 flights.

There are not enough flights in each departure window to split Spirit's DTW to BOS record by time of day without the percentages moving on noise. The headline rate of 77.9% is the reliable figure here.

Across the year

Spirit on DTW to BOS through the year

Jul–Sep 202577 flights83.1%
Oct–Dec 202563 flights73.0%
Apr–Jun 202614 flights—

Scale runs 65% to 90%. Rows with fewer than 30 flights show a dash.

Monthly volumes are too low here to break the year into twelve reliable readings. What the twelve-month total says is 77.9% on time across 154 flights.

Split by quarter, Spirit on DTW to BOS logged 77 flights in Jul–Sep 2025, 63 flights in Oct–Dec 2025 and 14 flights in Apr–Jun 2026. Fewer than three of those quarters carried the 30 completed flights this site needs before printing a rate, so the 77.9% annual figure is the one to use.

Delay causes

Why Spirit runs late on this route

One category carries most of the weight here. National Airspace System accounts for 62% of the 2,028 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
62%
Late-arriving aircraft
31%
Carrier
6%
Security
1%

62% 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 1,267 minutes out of 2,028, against a national NAS share of 21%. The split is drawn from 2,028 reported delay minutes.

Cancellations are rare at 0.00%, below the national 1.81% and low enough to earn the plus on the grade. Almost no flights are called off; the risk here is arriving late, not not arriving.

Connections and stage length

What a delay here costs

For anyone connecting, the number to weigh is not the on-time rate but the tail behind it. 9.1% 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.

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 82.6% on time across 155 flights, 5 points above 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.

One caution: this is a thin sample. 154 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 Spirit on DTW to BOS

Put together: treat all of this as provisional. 154 flights over twelve months is enough to clear this site's floor and not enough to be confident to better than a couple of points. The 77.9% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 154 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