Carrier route record

DLBOS→RDU

Delta Air Lines · Boston to Raleigh

Flights: 1,437
Period: July 2025 to June 2026
Share of route: 51%
Carriers: 4

Historical statistics for July 2025 to June 2026, not live status. For today’s flights, check with Delta Air Lines.

Delta on BOS to RDU lands a B, level with the national rate of 77.6%. Roughly one flight in four arrives 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 1,437 flights, with a median arrival 10 minutes early.

The US average over the same twelve months is 77.6%, so there is little to separate Delta on BOS to RDU from the country as a whole. The variation that matters here is internal: which carrier, and what time of day.

On time

77.6%

Arrivals under 15 minutes late, of 1,402 completed flights

Avg delay

86 min

Across delayed arrivals only, not all flights

Cancelled

2.44%

National rate is 1.81%

Whole route

76.3%

Every carrier on BOS to RDU, 2,816 flights

These figures cover 1,437 flights between July 2025 and June 2026. Beyond the headline rate, 11.6% 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

Delta against every carrier on BOS to RDU

Delta flew 1,437 of the 2,816 flights on BOS to RDU, most of the route. Its 77.6% on time is about level with the route as a whole at 76.3%. Ranked by on-time rate it is number two of four carriers on the route, where the range runs from Republic at 82.4% to JetBlue at 74.0%. Two of those carriers flew fewer than 365 flights here, so treat their positions as rough.

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.

On-time performance by carrier on BOS to RDU
Airline	Flights	On time	Avg delay	Cancelled	Grade
Republic Airwaysthin sample	136	82.4%	75 min	3.68%	B−
Delta Air Lines (this page)	1,437	77.6%	86 min	2.44%	B
Frontier Airlinesthin sample	159	74.7%	49 min	0.00%	C+
JetBlue Airways	1,084	74.0%	68 min	2.58%	C

Flight by flight

Delta flight numbers on BOS to RDU

Departure window

When Delta runs best on this route

Departure time matters more here than the choice of carrier. The gap between the best and worst window is 36 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–8am284 flights90.5%
8am–11am292 flights88.4%
11am–2pm230 flights82.5%
2pm–5pm149 flights81.9%
5pm–8pm293 flights63.5%
8pm–5am189 flights54.3%

Scale runs 45% to 95%. Rows with fewer than 30 flights show a dash.

The 8pm–5am window is where this operation falls apart: 54.3% on time, against 90.5% 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 293 flights scheduled in it.

Across the year

Delta on BOS to RDU through the year

Darker means more delays. Figures are on-time percentages.April best, September worst

April is the best month on the calendar at 86.5% on time. Shoulder season thins the schedule and takes the summer weather with it, and the operation gets its margin back. October was the busiest month here, with 142 flights.

Across the week, Saturday is the strongest day at 86.5% on time and Sunday the weakest at 70.5%. 16 points is a smaller lever than departure hour, but it is free.

Delay causes

Why Delta runs late on this route

One category carries most of the weight here. Late-arriving aircraft accounts for 50% of the 27,000 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
38%
National Airspace System
10%
Extreme weather
3%

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 27,000 reported delay minutes here, that single category outweighs weather by 19 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 27,074 reported delay minutes.

The largest share of delay minutes, 38%, 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 10,000 of the 27,000 delay minutes reported here.

Cancellations sit at 2.44% against a national 1.81%, which is ordinary. Diversions add another 0.00%.

Connections and stage length

What a delay here costs

For anyone connecting, the number to weigh is not the on-time rate but the tail behind it. 11.6% 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 80.4% on time across 1,436 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 1,437 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 Delta on BOS to RDU

Put together: the calendar is the biggest lever here, not the carrier or the hour. April runs 86.5% on time and September 67.7%, a swing of 19 points. If the dates move at all, move them out of September before you think about anything else. 1,402 completed flights over 12 months sit behind that.

Where to go next

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.

Key figures