Flight number record
DL 855
Delta Air Lines · Atlanta to Boston
- Route
- ATL → BOS
- Departs
- 09:10
- Flights
- 365
- Period
- September 2025 to August 2026
Historical statistics for September 2025 to August 2026, not live status. For today’s DL 855, check with Delta Air Lines.
DL 855 earns an A. More than four flights in five arrive inside the 15-minute window the DOT uses to define an on-time arrival, which puts it 8 points better than the national rate of 77.3%. When something does go wrong the average delay runs roughly 45 minutes. That rests on 365 flights, with a median arrival 7 minutes early.
Set against the rest of the country, DL 855's record is 8 points better than the US average of 77.3%. That gap is worth roughly 79 fewer late arrivals for every thousand flights.
Key figures
On time
85.2%
Arrivals under 15 minutes late, of 358 completed flights
Avg delay
43 min
Across delayed arrivals only, not all flights
Cancelled
1.92%
National rate is 1.89%
1 hour+ late
3.4%
National rate is 8.3%
These figures cover 365 flights between September 2025 and August 2026. The median arrival is 7 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.
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Schedule
When DL 855 flies
DL 855 flies ATL to BOS without a single fixed slot. Its most common scheduled departure was 09:10, used on 60 of 365 flights, with 10:05 (53 flights) next.
- Departs 09:1060 flights16.4%
- Departs 10:0553 flights14.5%
Scale runs 0% to 100%.
Share of scheduled departures at each local time. Times used on fewer than one flight in ten are not listed.
A 09:10 departure sits in the 8am–11am window. Across every US flight scheduled in that window the on-time rate is 83.9%, and DL 855 runs level with that at 85.2%. Early departures usually start with an aircraft that has not flown yet that day, which is most of why the window does well.
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Against the route
DL 855 next to ATL to BOS
Every carrier on ATL to BOS combined arrived on time 72.8% of the time across 5,054 flights, so DL 855 is 12 points ahead of it. Delta flew 3,731 flights on the same city pair under all its flight numbers, including this one, and those ran 74.4% on time. Across its whole network Delta Air Lines managed 81.1%, which this flight beats by 4 points.
| Compared with | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| DL 855 | 365 | 85.2% | 43 min | 1.92% | A |
| All Delta Air Lines on ATL–BOS | 3,731 | 74.4% | 61 min | 1.82% | C |
| All carriers on ATL–BOS | 5,054 | 72.8% | 66 min | 2.30% | C |
| Delta Air Lines, whole network | 1,039,517 | 81.1% | 71 min | 1.74% | B |
Across the year
DL 855 quarter by quarter
DL 855 did not run the same all year. Its best quarter was Apr–Jun 2026 at 93.4% on time and its weakest Jul–Sep 2025 at 76.7%, a swing of 17 points on roughly 73 flights a quarter. The twelve-month rate averages over that, so if you are flying in a weak quarter the quarter's own figure is the better guide.
- Jul–Sep 202530 flights76.7%
- Oct–Dec 202592 flights85.9%
- Jan–Mar 202690 flights83.5%
- Apr–Jun 202691 flights93.4%
- Jul–Sep 202662 flights78.3%
Scale runs 70% to 100%.
By weekday, DL 855 did best on Saturday at 91.8% on time and worst on Monday at 76.5%. Each day rests on about 52 flights, so a gap of 15 points is worth noticing but could still narrow in another year.
Arrival by arrival
How late DL 855 runs when it is late
The 53 late arrivals split 25 under half an hour, 16 between 30 and 60 minutes, and 12 an hour or more.
- 15+ min early89 flights24.9%
- Within 15 min216 flights60.3%
- 15–29 min late25 flights7.0%
- 30–59 min late16 flights4.5%
- 1–2 hours late9 flights2.5%
- 2+ hours late3 flights0.8%
Scale runs 0% to 100%.
Share of 358 completed flights by arrival against schedule.
A late pushback is often recovered here: of 64 departures that left 15 minutes late or more, 25 still arrived on time. 14 flights left on time and still arrived late.
The worst days
Worst days for DL 855
The latest arrival of the period was on 25 November 2025, 3 hours 11 minutes behind schedule; most of its delay minutes were filed as a late-arriving aircraft. On three of the five worst days the largest share was filed as carrier-caused (crew, maintenance, fuelling, baggage).
| Date | Arrived late by | Largest filed cause |
|---|---|---|
| 25 November 2025 | 3 hours 11 minutes | Late-arriving aircraft |
| 14 October 2025 | 2 hours 39 minutes | National Airspace System |
| 14 June 2026 | 2 hours 2 minutes | Carrier |
| 2 September 2025 | 1 hour 15 minutes | Carrier |
| 13 July 2026 | 1 hour 13 minutes | Carrier |
Delay causes
Why DL 855 runs late
Carrier accounts for 48% of the 2,260 delay minutes carriers reported here, and the remaining four split what is left.
- 48%Carrier
- 31%National Airspace System
- 19%Late-arriving aircraft
- 2%Extreme weather
The largest share of delay minutes, 48%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. It accounts for 1,075 of the 2,260 delay minutes reported here. The split is drawn from 2,260 delay minutes reported on DL 855.
Cancellations sit at 1.92% against a national 1.89%, which is ordinary. Diversions add another 0.00%.
Connections and routes
What a delay on this flight costs
Badly late arrivals are rare here: only 3.4% land an hour or more behind schedule, against 8.3% nationally. Connections built on this flight are about as safe as US domestic connections get, though a cancelled flight still ignores every layover you give it.
The 946 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.
Every one of the 365 flights under DL 855 in the data flew ATL to BOS. The number was not reused on any other city pair, which makes this a clean record of one route.
One caution: this is a thin sample. 365 flights over twelve months is enough to clear this site's floor but not enough to pin the rate down tightly, and a single bad week moves it by more than a point. Treat the grade as a rough reading.
What to do with this
Booking DL 855
For a booking, read DL 855 as 85.2% on time with 1.92% cancelled over 365 flights. Those are rates from the past twelve months, not a forecast for any particular day.
Related
Where to go next
- ATL to BOS, every carrier and departure
- BOS to ATL, the return direction
- Delta Air Lines 865 on the same route80.2%
- Delta Air Lines 726 on the same route66.3%
- Delta Air Lines 821 on the same route69.2%
- Delta Air Lines 987 on the same route89.9%
- Delta Air Lines 350 on the same route74.6%
- Delta Air Lines 2595 on the same route62.5%
- Hartsfield-Jackson Atlanta International (ATL) delay statistics
- Boston Logan International (BOS) delay statistics
- Delta Air Lines on-time record
- Every Delta Air Lines flight number with a record
- The most and least reliable flight numbers in the US
- Worst months to fly in the US, ranked by the data
A flight number here means Delta Air Lines’s own number as it reports to the DOT. How the figures are computed is on the methodology page.
Source: US DOT Bureau of Transportation Statistics, on-time performance data, September 2025 to August 2026. Last updated ; recomputed monthly. How this data is collected.