Route reliability record
RDU→BOS
Raleigh to Boston
- Flights
- 2,815
- Period
- July 2025 to June 2026
- Distance
- 612 mi
- Carriers
- 4
This route lands a B, about a point better than the national rate of 77.6%. About one flight in five arrive 15 minutes late or worse, and those flights are late by an hour and a half on average. That is a workable record, not a spotless one. That rests on 2,815 flights, of which Delta Air Lines flew 1,436 at 80.4% 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
78.8%
Arrivals under 15 minutes late, of 2,742 completed flights
Avg delay
82 min
Across delayed arrivals only, not all flights
Cancelled
2.59%
National rate is 1.81%
Best carrier
Delta
80.4% on time across 1,436 flights
These figures cover 2,815 flights between July 2025 and June 2026. Beyond the headline rate, 9.7% 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 RDU to BOS
The two carriers here are closely matched: 4 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.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| Frontier Airlinesthin sample | 159 | 80.5% | 56 min | 0.00% | B+ |
| Delta Air Lines | 1,436 | 80.4% | 87 min | 2.51% | B |
| Republic Airwaysthin sample | 137 | 80.0% | 94 min | 5.11% | B− |
| JetBlue Airways | 1,083 | 76.4% | 79 min | 2.77% | B |
No carrier stands out. Delta tops the table at 80.4%, 4 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 28 points, against 4 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am584 flights92.6%
- 8am–11am768 flights86.7%
- 11am–2pm368 flights74.7%
- 2pm–5pm453 flights64.2%
- 5pm–8pm371 flights72.8%
- 8pm–5am271 flights64.9%
Scale runs 55% to 100%. Rows with fewer than 30 flights show a dash.
Book the early departure. Flights leaving between 5am–8am arrive on time 92.6% of the time, against 64.2% for the afternoon window. That is 28 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 8am–11am window is the busiest, with 768 flights scheduled in it.
Across the year
When delays peak on this route
This route's year swings by 19 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 66.4%. August is the strongest month at 85.5%. Moving a flexible trip across that boundary buys 19 points. October was the busiest month here, with 291 flights.
Across the week, Saturday is the strongest day at 84.1% on time and Thursday the weakest at 75.8%. 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 44% of the 48,000 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.
- 44%Late-arriving aircraft
- 36%National Airspace System
- 19%Carrier
- 1%Extreme weather
44% 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 48,000 reported delay minutes here, that single category outweighs weather by 44 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 47,761 reported delay minutes.
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 17,000 minutes out of 48,000, against a national NAS share of 21%.
Cancellations run at 2.59%, against 1.81% nationally. That is about one flight in 40 cancelled outright. A cancelled flight is invisible in every on-time figure on this page, so the punctuality numbers above describe only the flights that actually operated.
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. 9.7% 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 612 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 76.3% on time across 2,816 flights, within 3 points 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 2,815 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. August runs 85.5% on time and September 66.4%, a swing of 19 points. If the dates move at all, move them out of September before you think about anything else. 2,742 completed flights over 12 months sit behind that.
Common questions
RDU to BOS questions
How often is RDU to BOS delayed?
About one flight in five arrive at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 21.2% of the 2,815 flights in this analysis, against 22.4% nationally. Delayed flights are late by an hour and a half on average.
Which airline is most reliable on RDU to BOS?
Delta Air Lines leads at 80.4% on time across 1,436 flights. JetBlue Airways is at the other end on 76.4%, a gap of 4 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 RDU to BOS?
The 5am–8am departure window is the strongest at 92.6% on time. The 2pm–5pm window is the weakest at 64.2%, 28 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 RDU to BOS?
September is the weakest month at 66.4% on time, compared with 85.5% in August. Across the year that is 19 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 RDU — the return legseparate record
- Raleigh-Durham International (RDU) delay statistics
- Boston Logan International (BOS) delay statistics
- Frontier Airlines on-time record80.5%
- Delta Air Lines on-time record80.4%
- Republic Airways on-time record80.0%
- Why the first flight of the morning is statistically safest
- The best time of day to fly, according to 7.04 million flight records
Direction matters. RDU to BOS and BOS to RDU 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.