Route reliability record
BOS→MDW
Boston to Chicago
- Flights
- 1,382
- Period
- July 2025 to June 2026
- Distance
- 861 mi
- Carriers
- 1
This route sits in the middle of the pack with a C. Close to three flights in four arrive on time by the DOT's definition, 5 points worse than the national rate of 77.6%. The late ones land about an hour behind schedule. That rests on 1,382 BOS to MDW flights, with a median arrival 3 minutes early.
Best time to fly BOS to MDW: a 5am–8am departure, ideally on a Saturday. Flights in that window arrived on time 92.9% of the time and Saturday flights 81.0%, against 73.1% for the route overall.
The national on-time rate over the same period is 77.6%, so this route runs 5 points behind the country as a whole. Across a thousand flights that is about 45 extra late arrivals.
Key figures
On time
73.1%
Arrivals under 15 minutes late, of 1,351 completed flights
Avg delay
62 min
Across delayed arrivals only, not all flights
Cancelled
1.81%
National rate is 1.81%
Best carrier
Southwest
73.1% on time across 1,382 flights
These figures cover 1,382 flights between July 2025 and June 2026. Beyond the headline rate, 9.2% 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 MDW
Only one carrier clears this site's 365-flight floor here, so there is no comparison to draw. The table below is the full picture.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| Southwest Airlines | 1,382 | 73.1% | 62 min | 1.81% | C |
Best ways to make this trip
The most reliable ways to fly Boston to Chicago
Every airline on this route and on the routes between nearby airports, ranked by how often a scheduled flight actually operated and arrived on time. 5 of the top 5 use a different airport at one end.
| Option | Airline | Success | On time | Cancelled | Best departure | Most punctual flight |
|---|---|---|---|---|---|---|
| 1. PVD → MDWProvidence to Chicago | Southwest Airlines | 83.2% | 84.6% | 1.68% | 5am–8am, Tue | — |
| 2. PVD → ORDProvidence to Chicago | American Airlines | 76.8% | 79.2% | 3.02% | 5am–8am, Sun | — |
| 3. BOS → ORDBoston to Chicago | United Airlines | 73.6% | 75.0% | 1.90% | 5am–8am, Tue | UA 1414 06:00 |
| 4. BOS → ORDBoston to Chicago | Envoy Air | 72.9% | 75.6% | 3.60% | 2pm–5pm, Mon | — |
| 5. BOS → ORDBoston to Chicago | JetBlue Airways | 71.9% | 73.6% | 2.25% | 5am–8am, Wed | B6 311 07:00 |
Success is the share of scheduled flights that operated and arrived less than 15 minutes late, so a cancelled flight counts against it. “(route)” means the best time comes from every carrier on the route rather than this airline alone.
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 59 points, against half a point between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am388 flights92.9%
- 8am–11am203 flights91.5%
- 11am–2pm160 flights78.0%
- 2pm–5pm252 flights68.3%
- 5pm–8pm314 flights45.0%
- 8pm–5am65 flights33.9%
Scale runs 25% to 100%. Rows with fewer than 30 flights show a dash.
The 8pm–5am window is where this operation falls apart: 33.9% on time, against 92.9% 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 5am–8am window is the busiest, with 388 flights scheduled in it.
Across the year
When delays peak on this route
This route's year swings by 28 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 September, when the on-time rate falls to 57.1%. January is the strongest month at 84.8%. Moving a flexible trip across that boundary buys 28 points. July was the busiest month here, with 172 flights.
Across the week, Saturday is the strongest day at 81.0% on time and Sunday the weakest at 65.7%. 15 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 59% of the 22,000 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.
- 59%Late-arriving aircraft
- 22%Carrier
- 17%National Airspace System
- 2%Extreme weather
59% 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 22,000 reported delay minutes here, that single category outweighs weather by 26 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 22,403 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 92.9% on time here.
Cancellations sit at 1.81% against a national 1.81%, which is ordinary. Diversions add another 0.43%.
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. 9.2% 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 861 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 67.4% on time across 1,381 flights, 6 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 6 points of difference.
The sample behind these figures is 1,382 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.
Work out the risk of missing a connection in MDW after this flight
What to do with this
Booking this route
Put together: the calendar is the biggest lever here, not the carrier or the hour. January runs 84.8% on time and September 57.1%, a swing of 28 points. If the dates move at all, move them out of September before you think about anything else. 1,351 completed flights over 12 months sit behind that.
Common questions
BOS to MDW questions
How often is BOS to MDW delayed?
About one flight in four arrives at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 26.9% of the 1,382 flights in this analysis, against 22.4% nationally. Delayed flights are late by about an hour on average.
How reliable is BOS to MDW compared with the rest of the country?
73.1% of flights arrive on time here against a national 77.6%, a difference of 5 points against it. That is worth a C on this site's grading scale.
What time of day has the fewest delays on BOS to MDW?
The 5am–8am departure window is the strongest at 92.9% on time. The 8pm–5am window is the weakest at 33.9%, 59 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 BOS to MDW?
September is the weakest month at 57.1% on time, compared with 84.8% in January. Across the year that is 28 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
- MDW to BOS — the return legseparate record
- Boston Logan International (BOS) delay statistics
- Chicago Midway International (MDW) delay statistics
- BOS to DCA, a related route74.0%
- ATL to MDW, a related route76.3%
- BOS to ORD, a related route72.7%
- Southwest Airlines on-time record73.1%
- Why the first flight of the morning is statistically safest
- How often a connection fails at the major US hubs
Direction matters. BOS to MDW and MDW to BOS are scored separately because they are separate operations, with different departure banks and different aircraft. Compare the return leg.
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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.