Route reliability record
MDW→BOS
Chicago to Boston
- Flights
- 1,381
- Period
- July 2025 to June 2026
- Distance
- 861 mi
- Carriers
- 1
This route draws a C. About one flight in three arrives at least 15 minutes late, and the typical late arrival is about an hour behind schedule. Build slack into anything you connect to. That rests on 1,381 MDW to BOS flights, with a median arrival right on schedule.
Best time to fly MDW to BOS: a 5am–8am departure, ideally on a Saturday. Flights in that window arrived on time 94.0% of the time and Saturday flights 78.3%, against 67.4% for the route overall.
The national on-time rate over the same period is 77.6%, so this route runs 10 points behind the country as a whole. Across a thousand flights that is about 102 extra late arrivals.
Key figures
On time
67.4%
Arrivals under 15 minutes late, of 1,364 completed flights
Avg delay
62 min
Across delayed arrivals only, not all flights
Cancelled
1.23%
National rate is 1.81%
Best carrier
Southwest
67.4% on time across 1,381 flights
These figures cover 1,381 flights between July 2025 and June 2026. Beyond the headline rate, 10.7% 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 MDW to BOS
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 | 1,381 | 67.4% | 62 min | 1.23% | C |
Best ways to make this trip
The most reliable ways to fly Chicago to Boston
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. ORD → BOSChicago to Boston | Envoy Air | 80.7% | 82.8% | 2.48% | 5am–8am, Thu | — |
| 2. MDW → PVDChicago to Providence | Southwest Airlines | 74.8% | 75.9% | 1.41% | 5am–8am, Wed | — |
| 3. ORD → BOSChicago to Boston | JetBlue Airways | 71.6% | 73.5% | 2.62% | 5am–8am, Wed | B6 312 08:40 |
| 4. ORD → BOSChicago to Boston | United Airlines | 67.3% | 68.6% | 1.87% | 5am–8am, Sat | UA 2067 07:30 |
| 5. ORD → BOSChicago to Boston | Delta Air Lines | 67.0% | 69.1% | 3.01% | 5am–8am, Fri | — |
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 45 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–8am232 flights94.0%
- 8am–11am277 flights83.1%
- 11am–2pm215 flights54.2%
- 2pm–5pm250 flights49.2%
- 5pm–8pm339 flights59.3%
- 8pm–5am68 flights60.6%
Scale runs 40% to 100%. Rows with fewer than 30 flights show a dash.
Book the early departure. Flights leaving between 5am–8am arrive on time 94.0% of the time, against 49.2% for the afternoon window. That is 45 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 339 flights scheduled in it.
Across the year
When delays peak on this route
This route's year swings by 26 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 March, when the on-time rate falls to 54.5%. February is the strongest month at 80.0%. Moving a flexible trip across that boundary buys 26 points. July was the busiest month here, with 172 flights.
Across the week, Saturday is the strongest day at 78.3% on time and Sunday the weakest at 60.8%. 18 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 27,000 reported delay minutes.
- 36%National Airspace System
- 31%Late-arriving aircraft
- 29%Carrier
- 2%Extreme weather
- 1%Security
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 9,880 minutes out of 27,000, against a national NAS share of 21%. The split is drawn from 27,407 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 94.0% on time here.
Cancellations sit at 1.23% against a national 1.81%, which is ordinary. Diversions add another 0.00%.
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. 10.7% 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 73.1% on time across 1,382 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.
The sample behind these figures is 1,381 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 BOS 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. February runs 80.0% on time and March 54.5%, a swing of 26 points. If the dates move at all, move them out of March before you think about anything else. 1,364 completed flights over 12 months sit behind that.
Common questions
MDW to BOS questions
How often is MDW to BOS delayed?
About one flight in three arrives at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 32.6% of the 1,381 flights in this analysis, against 22.4% nationally. Delayed flights are late by about an hour on average.
How reliable is MDW to BOS compared with the rest of the country?
67.4% of flights arrive on time here against a national 77.6%, a difference of 10 points against it. That is worth a C on this site's grading scale.
What time of day has the fewest delays on MDW to BOS?
The 5am–8am departure window is the strongest at 94.0% on time. The 2pm–5pm window is the weakest at 49.2%, 45 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 March delays on MDW to BOS?
March is the weakest month at 54.5% on time, compared with 80.0% in February. Across the year that is 26 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 MDW — the return legseparate record
- Chicago Midway International (MDW) delay statistics
- Boston Logan International (BOS) delay statistics
- MDW to ATL, a related route79.8%
- DCA to BOS, a related route71.4%
- MDW to PHX, a related route75.0%
- Southwest Airlines on-time record67.4%
- How often a connection fails at the major US hubs
- The best time of day to fly, according to 7.04 million flight records
Direction matters. MDW to BOS and BOS to MDW 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.