Route reliability record
BOS→ORD
Boston to Chicago
- Flights
- 7,637
- Period
- July 2025 to June 2026
- Distance
- 867 mi
- Carriers
- 6
This route sits in the middle of the pack with a C. About seven flights in ten arrive on time by the DOT's definition, 5 points worse than the national rate of 77.6%. The late ones land an hour and a half behind schedule. That rests on 7,637 flights, of which Envoy Air flew 445 at 75.6% on time.
Envoy Air is the most reliable of the six carriers covered here at 75.6% on time across 445 flights.
Key figures
On time
72.7%
Arrivals under 15 minutes late, of 7,376 completed flights
Avg delay
84 min
Across delayed arrivals only, not all flights
Cancelled
2.91%
National rate is 1.81%
Best carrier
Envoy
75.6% on time across 445 flights
These figures cover 7,637 flights between July 2025 and June 2026. Beyond the headline rate, 12.0% 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 BOS to ORD
The choice of carrier is not cosmetic here. Envoy Air arrives on time 75.6% of the time; Delta Air Lines manages 65.2%. Sample sizes sit next to every figure, because a two-point gap across 962 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| Envoy Air | 445 | 75.6% | 91 min | 3.60% | B− |
| United Airlines | 2,678 | 75.0% | 85 min | 1.90% | B |
| JetBlue Airways | 533 | 73.6% | 68 min | 2.25% | C |
| American Airlines | 2,125 | 73.4% | 93 min | 2.82% | C |
| Republic Airways | 894 | 70.4% | 81 min | 5.93% | C− |
| Delta Air Lines | 962 | 65.2% | 75 min | 3.12% | C− |
Republic Airways cancels 5.9% 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 36 points, against 10 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am1,685 flights87.6%
- 8am–11am1,215 flights85.5%
- 11am–2pm1,410 flights78.7%
- 2pm–5pm1,707 flights63.1%
- 5pm–8pm1,270 flights51.5%
- 8pm–5am350 flights53.4%
Scale runs 45% to 95%. Rows with fewer than 30 flights show a dash.
The 5pm–8pm window is where this operation falls apart: 51.5% on time, against 87.6% 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 2pm–5pm window is the busiest, with 1,707 flights scheduled in it.
Across the year
When delays peak on this route
This route's year swings by 19 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.
Delays peak in October, when the on-time rate falls to 64.0%. February is the strongest month at 83.4%. Moving a flexible trip across that boundary buys 19 points. June was the busiest month here, with 750 flights.
Across the week, Tuesday is the strongest day at 77.2% on time and Sunday the weakest at 67.7%. 10 points is a smaller lever than departure hour, but it is free.
Delay causes
Why this route gets delayed
Carriers report a reason for every delay minute they cause, in five DOT categories. The split below is by minutes, not by number of flights, so a handful of very long weather delays weighs as much as many short ones. It covers 169,000 reported delay minutes.
- 40%Late-arriving aircraft
- 36%National Airspace System
- 20%Carrier
- 3%Extreme weather
- 0%Security
40% 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 169,000 reported delay minutes here, that single category outweighs weather by 12 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 168,736 reported delay minutes.
36% 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 61,000 minutes out of 169,000, against a national NAS share of 21%.
Cancellations run at 2.91%, against 1.81% nationally. That is roughly 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 actually costs
For anyone connecting, the number to weigh is not the on-time rate but the tail behind it. 12.0% 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 67.6% on time across 7,642 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 7,637 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 delay figures matter less here than the 2.91% cancellation rate. A late arrival costs you an hour and a half; 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. 7,376 completed flights over 12 months sit behind that.
Common questions
BOS to ORD questions
How often is BOS to ORD delayed?
Roughly one flight in four arrive at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 27.3% of the 7,637 flights in this analysis, against 22.4% nationally. Delayed flights are late by an hour and a half on average.
Which airline is most reliable on BOS to ORD?
Envoy Air leads at 75.6% on time across 445 flights. Delta Air Lines is at the other end on 65.2%, a gap of 10 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 BOS to ORD?
The 5am–8am departure window is the strongest at 87.6% on time. The 5pm–8pm window is the weakest at 51.5%, 36 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 October delays on BOS to ORD?
October is the weakest month at 64.0% on time, compared with 83.4% in February. Across the year that is 19 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
- ORD to BOS — the return legseparate record
- Boston Logan International (BOS) delay statistics
- Chicago O'Hare International (ORD) delay statistics
- Envoy Air on-time record75.6%
- United Airlines on-time record75.0%
- JetBlue Airways on-time record73.6%
- 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. BOS to ORD and ORD to BOS 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.