Flight number record
DL 518
Delta Air Lines · Atlanta to Boston
- Route
- ATL → BOS
- Departs
- 16:52
- Flights
- 279
- Period
- September 2025 to August 2026
Historical statistics for September 2025 to August 2026, not live status. For today’s DL 518, check with Delta Air Lines.
DL 518 earns an F, which is as low as this site's scale goes for a reason. Only 52.7% of flights arrive inside the 15-minute window, 25 points worse than the national rate of 77.3%. Late arrivals average a little over an hour. Treat any tight connection here as a coin flip. That rests on 279 flights, with a median arrival 12 minutes late.
The national on-time rate over the same period is 77.3%, so DL 518 runs 25 points behind the country as a whole. Across a thousand flights that is about 246 extra late arrivals.
Key figures
On time
52.7%
Arrivals under 15 minutes late, of 275 completed flights
Avg delay
70 min
Across delayed arrivals only, not all flights
Cancelled
1.43%
National rate is 1.89%
1 hour+ late
20.0%
National rate is 8.3%
These figures cover 279 flights between September 2025 and August 2026. Beyond the headline rate, 20.0% of arrivals land a full hour or more behind schedule, against 8.3% nationally.
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Schedule
When DL 518 flies
DL 518 flies ATL to BOS without a single fixed slot. Its most common scheduled departure was 16:52, used on 56 of 279 flights, with 16:20 (51 flights) and 16:25 (38 flights) next.
- Departs 16:5256 flights20.1%
- Departs 16:2051 flights18.3%
- Departs 16:2538 flights13.6%
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 16:52 departure sits in the 2pm–5pm window. Across every US flight scheduled in that window the on-time rate is 71.9%, and DL 518 runs 19 points worse at 52.7%. Midday slots inherit some of the morning's delays without yet carrying the full weight of the evening's.
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Against the route
DL 518 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 518 is 20 points behind 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 trails by 28 points.
| Compared with | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| DL 518thin sample | 279 | 52.7% | 70 min | 1.43% | F |
| 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 518 quarter by quarter
DL 518 did not run the same all year. Its best quarter was Oct–Dec 2025 at 61.0% on time and its weakest Jul–Sep 2026 at 36.7%, a swing of 24 points on roughly 70 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 202522 flights—
- Oct–Dec 202578 flights61.0%
- Jan–Mar 202641 flights57.5%
- Apr–Jun 202677 flights57.9%
- Jul–Sep 202661 flights36.7%
Scale runs 30% to 65%. Rows with fewer than 30 flights show a dash.
By weekday, DL 518 did best on Wednesday at 68.4% on time and worst on Monday at 41.3%. Each day rests on about 40 flights, so a gap of 27 points is worth noticing but could still narrow in another year.
Arrival by arrival
How late DL 518 runs when it is late
The 130 late arrivals split 35 under half an hour, 40 between 30 and 60 minutes, and 55 an hour or more.
- 15+ min early34 flights12.4%
- Within 15 min111 flights40.4%
- 15–29 min late35 flights12.7%
- 30–59 min late40 flights14.5%
- 1–2 hours late31 flights11.3%
- 2+ hours late24 flights8.7%
Scale runs 0% to 100%.
Share of 275 completed flights by arrival against schedule.
Time lost at the gate mostly stays lost. Of 116 departures that left 15 minutes late or more, only 12 made it up before arrival. In the other direction, 26 flights left on time yet arrived 15 minutes late or more, so that delay built up after pushback: in the air, in a holding pattern or on the ground at BOS.
The worst days
Worst days for DL 518
The latest arrival of the period was on 17 March 2026, 5 hours 29 minutes behind schedule; most of its delay minutes were filed as carrier-caused (crew, maintenance, fuelling, baggage). The same cause led on three of the five worst days.
| Date | Arrived late by | Largest filed cause |
|---|---|---|
| 17 March 2026 | 5 hours 29 minutes | Carrier |
| 17 July 2026 | 5 hours 10 minutes | Carrier |
| 18 June 2026 | 3 hours 52 minutes | National Airspace System |
| 10 August 2026 | 3 hours 50 minutes | Carrier |
| 7 August 2026 | 3 hours 25 minutes | National Airspace System |
Delay causes
Why DL 518 runs late
National Airspace System accounts for 52% of the 9,124 delay minutes carriers reported here, and the remaining four split what is left.
- 52%National Airspace System
- 37%Carrier
- 9%Late-arriving aircraft
- 2%Extreme weather
- 1%Security
The largest share of delay minutes, 37%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. It accounts for 3,393 of the 9,124 delay minutes reported here. The split is drawn from 9,124 delay minutes reported on DL 518.
Cancellations sit at 1.43% against a national 1.89%, which is ordinary. Diversions add another 0.00%.
Connections and routes
What a delay on this flight costs
20.0% of arrivals land a full hour or more behind schedule, against 8.3% nationally. Ninety minutes is the honest minimum for a connection here, and two hours if the onward flight is on a separate ticket.
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.
The same number turns up on one other city pair in the data, including MCO to BOS (12), but none flew often enough under DL 518 to report a rate for. Carriers move flight numbers between routes, so the figures on this page apply to ATL to BOS only.
One caution: this is a thin sample. 279 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 518
For a booking, DL 518 is a flight to put a long connection behind. 20.0% of its completed flights arrived an hour or more late, which a short layover will not absorb. If the onward flight is on a separate ticket, the risk sits with you.
Related
Where to go next
- ATL to BOS, every carrier and departure
- BOS to ATL, the return direction
- Delta Air Lines 855 on the same route85.2%
- 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%
- 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
- How often a connection fails at the major US hubs
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.