Route reliability record
IAH→BWI
Houston to Baltimore
- Flights
- 1,311
- Period
- July 2025 to June 2026
- Distance
- 1,235 mi
- Carriers
- 4
This route sits in the middle of the pack with a B. Close to three flights in four arrive on time by the DOT's definition, 2 points worse than the national rate of 77.6%. The late ones land about an hour behind schedule. That rests on 1,311 IAH to BWI flights, of which United Airlines flew 814 at 77.9% on time.
Best time to fly IAH to BWI: a 11am–2pm departure, ideally on a Tuesday. Flights in that window arrived on time 83.2% of the time and Tuesday flights 81.6%, against 75.8% for the route overall.
The US average over the same twelve months is 77.6%, so there is little to separate this route from the country as a whole. The variation that matters here is internal: which carrier, and what time of day.
Key figures
On time
75.8%
Arrivals under 15 minutes late, of 1,289 completed flights
Avg delay
63 min
Across delayed arrivals only, not all flights
Cancelled
1.45%
National rate is 1.81%
Best carrier
United
77.9% on time across 814 flights
These figures cover 1,311 flights between July 2025 and June 2026. Beyond the headline rate, 8.1% 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 IAH to BWI
The two carriers here are closely matched: about a point separate the best from the worst. At that spread, schedule and price are better tie-breakers than reliability. Sample sizes are shown so you can see which rows are worth weighing.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| SkyWest Airlinesthin sample | 2 | 100.0% | — | 0.00% | A+ |
| United Airlines | 814 | 77.9% | 62 min | 0.61% | B+ |
| Spirit Airlines | 377 | 77.0% | 59 min | 2.12% | B |
| Frontier Airlinesthin sample | 118 | 55.9% | 74 min | 5.08% | D− |
No carrier stands out. United tops the table at 77.9%, about a point clear of the bottom, which is inside the range this kind of sample moves year to year.
Best ways to make this trip
The most reliable ways to fly Houston to Baltimore
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. 3 of the top 5 use a different airport at one end.
| Option | Airline | Success | On time | Cancelled | Best departure | Most punctual flight |
|---|---|---|---|---|---|---|
| 1. IAH → IADHouston to Washington | United Airlines | 80.1% | 80.4% | 0.43% | 5am–8am, Mon | UA 1549 07:20 |
| 2. IAH → BWIHouston to Baltimore | United Airlines | 77.4% | 77.9% | 0.61% | 5am–8am, Tue | — |
| 3. IAH → BWIHouston to Baltimore | Spirit Airlines | 75.4% | 77.0% | 2.12% | 5am–8am, Thu | — |
| 4. IAH → DCAHouston to Washington | United Airlines | 74.6% | 75.2% | 0.79% | 5am–8am, Tue | UA 512 07:30 |
| 5. HOU → BWIHouston to Baltimore | Southwest Airlines | 74.2% | 75.4% | 1.65% | 5am–8am, Tue | — |
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 25 points, against about a point between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am406 flights82.5%
- 8am–11am13 flights—
- 11am–2pm377 flights83.2%
- 2pm–5pm86 flights58.2%
- 5pm–8pm397 flights66.6%
- 8pm–5am32 flights68.8%
Scale runs 50% to 90%. Rows with fewer than 30 flights show a dash.
The best window here is not the first bank but the 11am–2pm slot at 83.2% on time, ahead of 2pm–5pm at 58.2%. Where the curve peaks mid-day rather than at dawn, the constraint is usually congestion at one end rather than the aircraft's own rotation. The 5am–8am window is the busiest, with 406 flights scheduled in it.
Across the year
When delays peak on this route
This route's year swings by 32 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.
July is the worst month at 56.3% on time, 32 points below January, the best at 88.4%. Summer afternoon convection and peak-season schedules land on the same weeks every year, so this is a pattern you can book around rather than a run of bad luck. November was the busiest month here, with 122 flights.
Across the week, Tuesday is the strongest day at 81.6% on time and Sunday the weakest at 68.1%. 14 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. Carrier accounts for 43% of the 20,000 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%Carrier
- 32%Late-arriving aircraft
- 19%National Airspace System
- 6%Extreme weather
- 0%Security
The largest share of delay minutes, 43%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. Unlike weather, that is a management outcome, and it is the category where the gap between two carriers on the same schedule is genuinely earned. It accounts for 8,332 of the 20,000 delay minutes reported here. The split is drawn from 19,573 reported delay minutes.
Cancellations sit at 1.45% against a national 1.81%, which is ordinary. Diversions add another 0.23%.
Connections and stage length
What a delay here actually costs
8.1% of arrivals land an hour or more late, close to the national 8.1%. That is the figure that decides a connection, and it says a 60 to 75 minute layover is reasonable here while anything under 45 minutes is a bet. Most delays on this route last about an hour, which a normal layover absorbs.
The 1,235 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 79.8% on time across 1,311 flights, 4 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 4 points of difference.
The sample behind these figures is 1,311 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 BWI 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 88.4% on time and July 56.3%, a swing of 32 points. If the dates move at all, move them out of July before you think about anything else. 1,289 completed flights over 12 months sit behind that.
Common questions
IAH to BWI questions
How often is IAH to BWI 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 24.2% of the 1,311 flights in this analysis, against 22.4% nationally. Delayed flights are late by about an hour on average.
Which airline is most reliable on IAH to BWI?
United Airlines leads at 77.9% on time across 814 flights. Spirit Airlines is at the other end on 77.0%, a gap of about a point. 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 IAH to BWI?
The 11am–2pm departure window is the strongest at 83.2% on time. The 2pm–5pm window is the weakest at 58.2%, 25 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 July delays on IAH to BWI?
July is the weakest month at 56.3% on time, compared with 88.4% in January. Across the year that is 32 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
- BWI to IAH — the return legseparate record
- George Bush Intercontinental (IAH) delay statistics
- Baltimore/Washington International Thurgood Marshall (BWI) delay statistics
- United Airlines on IAH to BWI77.9%
- Spirit Airlines on IAH to BWI77.0%
- Frontier Airlines on IAH to BWI55.9%
- IAH to ORD, a related route74.8%
- ATL to BWI, a related route75.6%
- IAH to DFW, a related route75.0%
- SkyWest Airlines on-time record100.0%
- United Airlines on-time record77.9%
- Spirit Airlines on-time record77.0%
- The best time of day to fly, according to 7.04 million flight records
- Worst months to fly in the US, ranked by the data
Direction matters. IAH to BWI and BWI to IAH 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.