Carrier route record

YXSTL→BOS

Republic Airways · St. Louis to Boston

Flights: 258
Period: July 2025 to June 2026
Share of route: 16%
Carriers: 3

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

Republic on STL to BOS lands a B−, 2 points worse than the national rate of 77.6%. About one flight in four arrives 15 minutes late or worse, and those flights are late by an hour and a half on average. That is a workable record, not a spotless one. That rests on 258 flights. The strongest carrier on the route with a full sample, Envoy Air, flew 418 at 75.9% on time.

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

On time

76.0%

Arrivals under 15 minutes late, of 250 completed flights

Avg delay

88 min

Across delayed arrivals only, not all flights

Cancelled

3.10%

National rate is 1.81%

Whole route

70.3%

Every carrier on STL to BOS, 1,610 flights

These figures cover 258 flights between July 2025 and June 2026. Beyond the headline rate, 8.4% 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

Republic against every carrier on STL to BOS

Republic flew 258 of the 1,610 flights on STL to BOS, about 16% of it. Its 76.0% on time is 6 points better than the route as a whole, which runs 70.3%. Ranked by on-time rate it is first of three carriers on the route, where the range runs from Republic at 76.0% to Southwest at 66.3%.

The choice of carrier is not cosmetic here. Envoy Air arrives on time 75.9% of the time; Southwest Airlines manages 66.3%. Sample sizes sit next to every figure, because a two-point gap across 934 flights means less than a ten-point one.

On-time performance by carrier on STL to BOS
Airline	Flights	On time	Avg delay	Cancelled	Grade
Republic Airways (this page)thin sample	258	76.0%	88 min	3.10%	B−
Envoy Air	418	75.9%	79 min	1.67%	B
Southwest Airlines	934	66.3%	59 min	0.96%	C+

Envoy leads Southwest by 10 points. Real, but small enough that a better departure time on the weaker carrier can outweigh it.

Departure window

When Republic runs best on this route

Departure time matters more here than the choice of carrier. The gap between the best and worst window is 26 points, against 10 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.

5am–8am—
8am–11am34 flights87.9%
11am–2pm155 flights76.0%
2pm–5pm7 flights—
5pm–8pm28 flights—
8pm–5am34 flights61.8%

Scale runs 55% to 95%. Rows with fewer than 30 flights show a dash.

The 8pm–5am window is where this operation falls apart: 61.8% on time, against 87.9% for the 8am–11am 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 11am–2pm window is the busiest, with 155 flights scheduled in it.

Across the year

Republic on STL to BOS through the year

Jul–Sep 202524 flights—
Oct–Dec 202558 flights86.0%
Jan–Mar 202682 flights76.6%
Apr–Jun 202694 flights68.8%

Scale runs 60% 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 76.0% on time across 258 flights.

Republic on STL to BOS did not run the same all year. Its best quarter was Oct–Dec 2025 at 86.0% on time and its weakest Apr–Jun 2026 at 68.8%, a swing of 17 points on roughly 86 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.

Across the week, Friday is the strongest day at 84.6% on time and Thursday the weakest at 70.3%. 14 points is a smaller lever than departure hour, but it is free.

Delay causes

Why Republic runs late on this route

One category carries most of the weight here. Late-arriving aircraft accounts for 56% of the 5,297 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
56%
National Airspace System
23%
Security
10%
Carrier
8%
Extreme weather
3%

56% 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 5,297 reported delay minutes here, that single category outweighs weather by 21 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 5,297 reported delay minutes.

The practical consequence: the 8am–11am departure is the one that starts clean. Its aircraft has no earlier leg to be late from, which is exactly why that window shows 87.9% on time here.

Cancellations run at 3.10%, against 1.81% nationally. That is about one flight in 30 cancelled outright. A cancelled flight is invisible in every on-time figure on this page, so the punctuality numbers above describe only the flights that actually operated.

Connections and stage length

What a delay here costs

8.4% 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 an hour and a half, which a normal layover absorbs.

The 1,047 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 82.3% on time across 258 flights, 6 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 6 points of difference.

One caution: this is a thin sample. 258 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 Republic on STL to BOS

Put together: the delay figures matter less here than the 3.10% cancellation rate. A late arrival costs you an hour and a half; a cancelled flight costs you the day. Book the 8am–11am departure so there is still a schedule behind you if it goes wrong, and treat a same-day connection as optimistic. 250 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