Route reliability record
ORD→BOS
Chicago to Boston
- Flights
- 7,642
- Period
- July 2025 to June 2026
- Distance
- 867 mi
- Carriers
- 6
This route draws a C. About one flight in three arrive 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 7,642 flights, of which Envoy Air flew 444 at 82.8% on time.
Envoy Air is the most reliable of the six carriers covered here at 82.8% on time across 444 flights.
Key figures
On time
67.6%
Arrivals under 15 minutes late, of 7,412 completed flights
Avg delay
78 min
Across delayed arrivals only, not all flights
Cancelled
2.79%
National rate is 1.81%
Best carrier
Envoy
82.8% on time across 444 flights
These figures cover 7,642 flights between July 2025 and June 2026. Beyond the headline rate, 14.5% 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
Which airline is most reliable on ORD to BOS
The choice of carrier is not cosmetic here. Envoy Air arrives on time 82.8% of the time; American Airlines manages 59.9%. Sample sizes sit next to every figure, because a two-point gap across 2,126 flights means less than a ten-point one.
| 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 | 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
The best time of day to leave
Departure time matters more here than the choice of carrier. The gap between the best and worst window is 32 points, against 23 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am1,536 flights86.4%
- 8am–11am1,429 flights78.1%
- 11am–2pm1,095 flights61.9%
- 2pm–5pm1,452 flights54.9%
- 5pm–8pm1,425 flights57.4%
- 8pm–5am705 flights60.4%
Scale runs 45% to 90%. Rows with fewer than 30 flights show a dash.
Book the early departure. Flights leaving between 5am–8am arrive on time 86.4% of the time, against 54.9% for the afternoon window. That is 32 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 5am–8am window is the busiest, with 1,536 flights scheduled in it.
Across the year
When delays peak on this route
This route's year swings by 20 points from best month to worst, which is wide. An annual average tells you very little about the week you are actually flying, so read the strip rather than the headline if your dates are fixed.
May is the best month on the calendar at 76.6% on time. Shoulder season thins the schedule and takes the summer weather with it, and the operation gets its margin back. June was the busiest month here, with 751 flights.
Across the week, Saturday is the strongest day at 75.0% on time and Sunday the weakest at 64.3%. 11 points is a smaller lever than departure hour, but it is free.
Delay causes
Why this route gets delayed
One category carries most of the weight here. Late-arriving aircraft accounts for 43% of the 187,000 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.
- 43%Late-arriving aircraft
- 33%National Airspace System
- 19%Carrier
- 5%Extreme weather
- 0%Security
43% 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 187,000 reported delay minutes here, that single category outweighs weather by 9 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 186,626 reported delay minutes.
33% 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 62,000 minutes out of 187,000, against a national NAS share of 21%.
Cancellations run at 2.79%, 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 actually costs
For anyone connecting, the number to weigh is not the on-time rate but the tail behind it. 14.5% 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 72.7% on time across 7,637 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.
The sample behind these figures is 7,642 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 this route
Put together: the calendar is the biggest lever here, not the carrier or the hour. May runs 76.6% on time and September 56.2%, a swing of 20 points. If the dates move at all, move them out of September before you think about anything else. 7,412 completed flights over 12 months sit behind that.
Common questions
ORD to BOS questions
How often is ORD to BOS delayed?
About one flight in three arrive at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 32.4% of the 7,642 flights in this analysis, against 22.4% nationally. Delayed flights are late by a little over an hour on average.
Which airline is most reliable on ORD to BOS?
Envoy Air leads at 82.8% on time across 444 flights. American Airlines is at the other end on 59.9%, a gap of 23 points. Sample size matters as much as the percentage: a rate built from a few hundred flights moves around far more than one built from ten thousand.
What time of day has the fewest delays on ORD to BOS?
The 5am–8am departure window is the strongest at 86.4% on time. The 2pm–5pm window is the weakest at 54.9%, 32 points behind. Later departures inherit delays from earlier flights the same aircraft has already flown, which is why the curve slopes the way it does.
How bad are September delays on ORD to BOS?
September is the weakest month at 56.2% on time, compared with 76.6% in May. Across the year that is 20 points between the best and worst months. Moving flexible dates out of that month is one of the few things that reliably helps.
Related
Where to go next
- BOS to ORD — the return legseparate record
- Chicago O'Hare International (ORD) delay statistics
- Boston Logan International (BOS) delay statistics
- Envoy Air on-time record82.8%
- JetBlue Airways on-time record73.5%
- Republic Airways on-time record70.3%
- Why the first flight of the morning is statistically safest
- The best time of day to fly, according to 7.04 million flight records
Direction matters. ORD to BOS and BOS to ORD are scored separately because they are separate operations, with different departure banks and different aircraft. Compare the return leg.
Source: US DOT Bureau of Transportation Statistics, on-time performance data, July 2025 to June 2026. Updated monthly. How this data is collected.