Carrier route record

AAORD→BOS

American Airlines · Chicago to Boston

Flights: 2,126
Period: July 2025 to June 2026
Share of route: 28%
Carriers: 6

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

American on ORD to BOS draws a D. Roughly one flight in two arrives at least 15 minutes late, and the typical late arrival is a little over an hour behind schedule. Build slack into anything you connect to. That rests on 2,126 flights. The strongest carrier on the route with a full sample, Envoy Air, flew 444 at 82.8% on time.

Envoy Air is the most reliable of the five carriers covered here at 82.8% on time across 444 flights.

On time

59.9%

Arrivals under 15 minutes late, of 2,061 completed flights

Avg delay

75 min

Across delayed arrivals only, not all flights

Cancelled

2.82%

National rate is 1.81%

Whole route

67.6%

Every carrier on ORD to BOS, 7,642 flights

These figures cover 2,126 flights between July 2025 and June 2026. Beyond the headline rate, 17.9% 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

American against every carrier on ORD to BOS

American flew 2,126 of the 7,642 flights on ORD to BOS, about 28% of it. Its 59.9% on time is 8 points worse than the route as a whole, which runs 67.6%. Ranked by on-time rate it is last of six carriers on the route, where the range runs from Envoy at 82.8% to American at 59.9%.

The choice of carrier is not cosmetic here. Envoy Air arrives on time 82.8% of the time; United Airlines manages 68.6%. Sample sizes sit next to every figure, because a two-point gap across 2,680 flights means less than a ten-point one.

On-time performance by carrier on ORD to BOS
Airline	Flights	On time	Avg delay	Cancelled	Grade
Envoy Air	444	82.8%	69 min	2.48%	B
JetBlue Airways	534	73.5%	83 min	2.62%	C
Republic Airways	896	70.3%	73 min	5.47%	C−
Delta Air Lines	962	69.1%	88 min	3.01%	C−
United Airlines	2,680	68.6%	78 min	1.87%	C
American Airlines (this page)	2,126	59.9%	75 min	2.82%	D

Republic Airways cancels 5.5% 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 American runs best on this route

Departure time matters more here than the choice of carrier. The gap between the best and worst window is 38 points, against 14 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.

5am–8am213 flights85.2%
8am–11am338 flights73.2%
11am–2pm399 flights57.9%
2pm–5pm332 flights47.4%
5pm–8pm569 flights52.8%
8pm–5am275 flights55.7%

Scale runs 40% to 90%. Rows with fewer than 30 flights show a dash.

Book the early departure. Flights leaving between 5am–8am arrive on time 85.2% of the time, against 47.4% for the afternoon window. That is 38 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 5pm–8pm window is the busiest, with 569 flights scheduled in it.

Across the year

American on ORD to BOS through the year

Darker means more delays. Figures are on-time percentages.November best, March worst

November is the best month on the calendar at 72.7% on time. Shoulder season thins the schedule and takes the summer weather with it, and the operation gets its margin back. May was the busiest month here, with 257 flights.

Across the week, Saturday is the strongest day at 68.6% on time and Monday the weakest at 53.3%. 15 points is a smaller lever than departure hour, but it is free.

Delay causes

Why American runs late on this route

One category carries most of the weight here. Late-arriving aircraft accounts for 49% of the 62,000 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
49%
National Airspace System
26%
Carrier
21%
Extreme weather
5%
Security
0%

49% 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 62,000 reported delay minutes here, that single category outweighs weather by 10 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 62,188 reported delay minutes.

The practical consequence: the 5am–8am departure is the one that starts clean. Its aircraft has no earlier leg to be late from, which is exactly why that window shows 85.2% on time here.

Cancellations run at 2.82%, against 1.81% nationally. That is roughly one flight in 40 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

For anyone connecting, the number to weigh is not the on-time rate but the tail behind it. 17.9% 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 867 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 73.4% on time across 2,125 flights, 14 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 14 points of difference.

The sample behind these figures is 2,126 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 American on ORD to BOS

Put together: the delay figures matter less here than the 2.82% cancellation rate. A late arrival costs you a little over an hour; a cancelled flight costs you the day. Book the 5am–8am departure so there is still a schedule behind you if it goes wrong, and treat a same-day connection as optimistic. 2,061 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