Route reliability record
BWI→DEN
Baltimore to Denver
- Flights
- 2,867
- Period
- July 2025 to June 2026
- Distance
- 1,491 mi
- Carriers
- 3
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 2,867 flights, of which United Airlines flew 902 at 85.6% on time.
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
75.6%
Arrivals under 15 minutes late, of 2,824 completed flights
Avg delay
59 min
Across delayed arrivals only, not all flights
Cancelled
1.12%
National rate is 1.81%
Best carrier
United
85.6% on time across 902 flights
These figures cover 2,867 flights between July 2025 and June 2026. The median arrival is 3 minutes early, which is the part an average hides: most flights here are fine, and the on-time rate is decided by a tail of badly late ones. On-time means under 15 minutes late, the DOT's own threshold.
Carrier by carrier
Which airline is most reliable on BWI to DEN
The choice of carrier is not cosmetic here. United Airlines arrives on time 85.6% of the time; Southwest Airlines manages 71.7%. Sample sizes sit next to every figure, because a two-point gap across 1,905 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| United Airlines | 902 | 85.6% | 77 min | 0.55% | A+ |
| Southwest Airlines | 1,905 | 71.7% | 53 min | 1.42% | C |
| Frontier Airlinesthin sample | 60 | 50.0% | 87 min | 0.00% | F+ |
The spread between United and Southwest is 14 points, wide enough that it should decide the booking. On a hundred trips that is 14 more arrivals inside the on-time window.
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 14 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am359 flights85.9%
- 8am–11am906 flights87.8%
- 11am–2pm233 flights73.4%
- 2pm–5pm736 flights70.1%
- 5pm–8pm464 flights60.8%
- 8pm–5am169 flights56.0%
Scale runs 50% to 95%. Rows with fewer than 30 flights show a dash.
The 8pm–5am window is where this operation falls apart: 56.0% on time, against 87.8% for the 8am–11am 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 8am–11am window is the busiest, with 906 flights scheduled in it.
Across the year
When delays peak on this route
This route's year swings by 27 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.
December is the weak month at 61.9% on time, against 89.2% in October. Winter delays cluster: a single storm system can account for most of a month's shortfall, so an average December hides both very good weeks and genuinely unflyable days. July was the busiest month here, with 317 flights.
Across the week, Tuesday is the strongest day at 82.3% on time and Friday the weakest at 72.5%. 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 41,000 reported delay minutes.
- 33%National Airspace System
- 31%Late-arriving aircraft
- 29%Carrier
- 7%Extreme weather
- 1%Security
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 13,000 minutes out of 41,000, against a national NAS share of 21%. The split is drawn from 40,728 reported delay minutes.
The practical consequence: the 8am–11am departure is the one that starts clean. Its aircraft has no earlier leg to be late from, which is exactly why that window shows 87.8% on time here.
Cancellations sit at 1.12% against a national 1.81%, which is ordinary. Diversions add another 0.38%.
Connections and stage length
What a delay here actually costs
7.0% 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 are the about an hour kind, which a normal layover absorbs.
The 1,491 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 runs 76.8% on time across 2,868 flights, within about a point of this direction. The two legs are scored separately because they usually differ; on this city pair they happen not to.
The sample behind these figures is 2,867 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. October runs 89.2% on time and December 61.9%, a swing of 27 points. If the dates move at all, move them out of December before you think about anything else. 2,824 completed flights over 12 months sit behind that.
Common questions
BWI to DEN questions
How often is BWI to DEN delayed?
About 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 24.4% of the 2,867 flights in this analysis, against 22.4% nationally. Delayed flights are late by about an hour on average.
Which airline is most reliable on BWI to DEN?
United Airlines leads at 85.6% on time across 902 flights. Southwest Airlines is at the other end on 71.7%, a gap of 14 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 BWI to DEN?
The 8am–11am departure window is the strongest at 87.8% on time. The 8pm–5am window is the weakest at 56.0%, 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 December delays on BWI to DEN?
December is the weakest month at 61.9% on time, compared with 89.2% in October. Across the year that is 27 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
- DEN to BWI — the return legseparate record
- Baltimore/Washington International Thurgood Marshall (BWI) delay statistics
- Denver International (DEN) delay statistics
- United Airlines on-time record85.6%
- Southwest Airlines on-time record71.7%
- Frontier Airlines on-time record50.0%
- The best time of day to fly, according to 7.04 million flight records
- Do budget airlines really get delayed more? The numbers
Direction matters. BWI to DEN and DEN to BWI 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.