Route reliability record

DEN→BWI

Denver to Baltimore

Flights: 2,868
Period: July 2025 to June 2026
Distance: 1,491 mi
Carriers: 3

This route lands a B, about a point worse than the national rate of 77.6%. About one flight in four arrive 15 minutes late or worse, and those flights are late by roughly 55 minutes on average. That is a workable record, not a spotless one. That rests on 2,868 flights, of which United Airlines flew 901 at 80.6% 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.

On time

76.8%

Arrivals under 15 minutes late, of 2,822 completed flights

Avg delay

53 min

Across delayed arrivals only, not all flights

Cancelled

1.22%

National rate is 1.81%

Best carrier

United

80.6% on time across 901 flights

These figures cover 2,868 flights between July 2025 and June 2026. The median arrival is 4 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 DEN to BWI

The two carriers here are closely matched: 6 points 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.

On-time performance by carrier on DEN to BWI
Airline	Flights	On time	Avg delay	Cancelled	Grade
United Airlines	901	80.6%	52 min	0.78%	B+
Southwest Airlines	1,907	75.1%	51 min	1.47%	B
Frontier Airlinesthin sample	60	71.7%	83 min	0.00%	C+

No carrier stands out. United tops the table at 80.6%, 6 points clear of the bottom, which is inside the range this kind of sample moves year to year.

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 35 points, against 6 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.

5am–8am465 flights93.7%
8am–11am640 flights85.9%
11am–2pm301 flights70.4%
2pm–5pm402 flights71.7%
5pm–8pm654 flights58.5%
8pm–5am406 flights81.9%

Scale runs 50% to 100%. Rows with fewer than 30 flights show a dash.

The 5pm–8pm window is where this operation falls apart: 58.5% on time, against 93.7% 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 5pm–8pm window is the busiest, with 654 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.

Darker means more delays. Figures are on-time percentages.January best, July worst

July is the worst month at 60.7% on time, 26 points below January, the best at 86.9%. 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. July was the busiest month here, with 317 flights.

Across the week, Wednesday is the strongest day at 81.1% on time and Thursday the weakest at 73.6%. 8 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 50% of the 34,000 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.

Late-arriving aircraft
50%
Carrier
31%
National Airspace System
18%
Extreme weather
1%

50% 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 34,000 reported delay minutes here, that single category outweighs weather by 50 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 34,384 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 93.7% on time here.

Cancellations sit at 1.22% against a national 1.81%, which is ordinary. Diversions add another 0.38%.

Connections and stage length

What a delay here actually costs

6.4% 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 roughly 55 minutes 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 75.6% on time across 2,867 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 2,868 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. January runs 86.9% on time and July 60.7%, a swing of 26 points. If the dates move at all, move them out of July before you think about anything else. 2,822 completed flights over 12 months sit behind that.

Common questions

DEN to BWI questions

How often is DEN to BWI 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 23.2% of the 2,868 flights in this analysis, against 22.4% nationally. Delayed flights are late by roughly 55 minutes on average.

Which airline is most reliable on DEN to BWI?

United Airlines leads at 80.6% on time across 901 flights. Southwest Airlines is at the other end on 75.1%, a gap of 6 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 DEN to BWI?

The 5am–8am departure window is the strongest at 93.7% on time. The 5pm–8pm window is the weakest at 58.5%, 35 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 DEN to BWI?

July is the weakest month at 60.7% on time, compared with 86.9% in January. 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.

Where to go next

Direction matters. DEN to BWI and BWI to DEN 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.

Key figures