Flight profile · Delta Air Lines
DL518
Atlanta (ATL) to Boston (BOS) · scheduled 7:55 PM – 10:30 PM
How DL518 performs
896 operations, July 2023 – July 2026.
DL518 arrived on time 69.2% of the time, against 76.6% for all ATL → BOS flights, so this departure is 7.4 percentage points worse than the route as a whole. Against Delta Air Lines’ own flights on this route it is 9.3 points worse.
Source: US DOT Bureau of Transportation Statistics · 896 operations, July 2023 – July 2026 · If DL518 is cancelled or significantly changed, DOT’s automatic refund rule may entitle you to your money back. The refund checker walks through eligibility.
Where DL518 is right now
A live reading, only if you ask for it. It is not part of the reliability record above.
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Against the rest of the route
| Flight or route | On time | Cancelled | Median delay | Severe | Flights |
|---|---|---|---|---|---|
| DL518 | 69.2% | 1.34% | -1 min | 12.9% | 896 |
| Delta Air Lines on ATL → BOS | 78.5% | 1.03% | -6 min | 6.9% | 11,240 |
| All ATL → BOS flights | 76.6% | 1.31% | -5 min | 8.2% | 15,476 |
Source: FlyerIntel analysis of US DOT BTS data · July 2023 – July 2026
Why DL518 runs late
Where US DOT attributed the delay minutes on this flight.
crew, maintenance, boarding and fueling, all within the carrier’s control
airspace and airport capacity, including weather-driven flow control
the inbound aircraft was late, so this flight started late
weather severe enough to stop this flight specifically
screening or terminal security incidents
Share of the delay minutes US DOT attributed to each cause for DL518 on ATL → BOS. Only delays of 15 minutes or more are attributed.
Source: US DOT Bureau of Transportation Statistics · Data covering July 2023 – July 2026
Does a late aircraft delay this flight?
How often the plane that flies DL518 comes in late, and what that does to the departure.
When the aircraft came in 15 or more minutes late, DL518 pushed back an average of 51 minutes late; when it came in on time or early, an average of 13 minutes late.
Each departure is matched to the flight the same aircraft flew into ATL just before it, using the tail number in the DOT file, 827 of 885 departures in all. A departure is left out when that flight is unknown, was cancelled or diverted, or the aircraft had sat for more than 12 hours. A flight the airline cancelled never left and is not in the count, and one flown by a substitute aircraft is matched to the aircraft that flew it, not to the one first planned.
Against the network at the same turn length
| Share of departures | Inbound landed 15+ late | Left 15+ late after a late inbound | Left 15+ late after an on-time inbound |
|---|---|---|---|
| DL518 | 17% | 71% | 25% |
| Network, same turn | 17% | 68% | 9% |
The schedule leaves a normal turn: enough time to clean and board if the aircraft is on time, little to spare if it is not.
The network row is every flight with a scheduled turn of 60 to 89 minutes. How often DL518’s aircraft landed 15 or more minutes late is about the same as the network’s and, once the aircraft was late, how often DL518 left 15 or more minutes late is about the same as the network’s.
More: Which Flight Numbers Pay for a Late Aircraft lists the flight numbers that pass a late aircraft on.
Source: US DOT Bureau of Transportation Statistics · Data covering July 2023 – July 2026
From pushback to gate
When it leaves ATL late, does that still matter by the time it reaches BOS?
DL518 pushes back an average of 21.7 minutes late and reaches the gate at BOS an average of 14.7 minutes late. The 7.0 minutes between those two figures are slack the published schedule already carries, which is why a late pushback on this flight does not reliably become a late arrival. Its 18.1 minutes on the taxiways at ATL is about what any departure from the airport in that hour spends.
On arrival at BOS, DL518 spends 10.1 min taxiing from touchdown to the gate — ground time a connecting passenger sits through before they can even leave the aircraft, on top of however late the flight itself ran. That is 1.2 minutes longer than a typical BOS arrival (9.0 min).
Departure delay is averaged over every pushback and arrival delay over every completed arrival, so the two counts differ by the flights that never reached BOS. Taxi-out is gate to wheels up and sits inside the scheduled block rather than on top of it; the comparison is 65,114 departures from ATL scheduled in the clock hour DL518 most often leaves in. Taxi-in is landing to gate, compared against every arrival FlyerIntel has on file at BOS (440,886 flights), not just DL518’s own. More on taxi time.
Source: FlyerIntel analysis of US DOT BTS data · July 2023 – July 2026
The hour it leaves ATL
Part of any flight’s record belongs to the clock rather than to the flight. DL518 has one departure time, so this is what that time is worth.
On-time arrival rate. 65,114 departures from ATL are scheduled in the 7 PM–8 PM hour over the period, against 1,012,247 across the whole day.
DL518 is scheduled out of ATL at 7:55 PM, in the 7 PM–8 PM bank. Departures from ATL in that hour arrive on time 70.3% of the time against 78.7% across the airport’s whole day — the slot alone is worth 8.4 points worse before anything about this particular flight is considered.
The two airport figures cover every departure from ATL to every destination, so they describe the slot rather than this journey — the like-for-like comparison against the route is above. Hours are scheduled local, and a number whose schedule moved between banks inside the period has no single hour and is not described here at all. Why the hour matters.
Source: FlyerIntel analysis of US DOT BTS data · July 2023 – July 2026 · Hours below 120 departures are not scored.
By day of week
Does DL518 run worse on particular days?
Wednesday is historically the most reliable day and Sunday the least, a gap of 12.4 percentage points.
Source: FlyerIntel analysis of US DOT BTS data · July 2023 – July 2026 · Days with fewer than 120 operations are not scored.
Other routes DL518 has flown
A flight number is a slot in a schedule, and carriers reassign it. These are the other city pairs this number served in the analysis period.
| Route | Operated | Flights | On time |
|---|---|---|---|
| MCO→BOS Orlando to Boston | April 19, 2025 – January 4, 2026 | 15 | — |
| ECP→ATL Panama City Beach to Atlanta | August 9, 2025 | 1 | — |
| BOS→LGA Boston to New York | May 10, 2025 – June 7, 2025 | 5 | — |
| MSP→OMA Minneapolis to Omaha | April 23, 2025 | 1 | — |
| OMA→MSP Omaha to Minneapolis | April 23, 2025 | 1 | — |
| ATL→GSP Atlanta to Greenville/Greer/Spartanburg | May 11, 2024 – June 1, 2024 | 5 | — |
| LGA→OMA New York to Omaha | May 4, 2024 | 1 | — |
| CLE→MSP Cleveland to Minneapolis | April 23, 2024 – May 1, 2024 | 4 | — |
| MSP→CLE Minneapolis to Cleveland | April 23, 2024 – May 1, 2024 | 4 | — |
| MSP→BIS Minneapolis to Bismarck | January 13, 2024 – March 2, 2024 | 11 | — |
| ATL→CAE Atlanta to Columbia | January 7, 2024 | 1 | — |
| CAE→ATL Columbia to Atlanta | January 7, 2024 | 1 | — |
| SFO→ATL San Francisco to Atlanta | December 16–30, 2023 | 13 | — |
| BOS→TPA Boston to Tampa | November 23, 2023 | 1 | — |
| XNA→ATL Fayetteville/Springdale/Rogers to Atlanta | November 4, 2023 | 1 | — |
Because the same number has served different journeys, the statistics above describe only the route DL518 currently operates. Blending them would produce an average of two different flights.
When it goes wrong
The average describes a usual day. This is the day that ruins a connection.
73 min late
against a median of 1 min early
DL518 has an average that understates its risk: a typical arrival is 1 min early, but the worst tenth are 74 minutes worse than that. If the trip has something unmissable at the end of it, the median is the wrong number to plan against.
Percentiles over 896 operations; cancelled and diverted flights are counted separately.
Source: US DOT Bureau of Transportation Statistics · Data covering July 2023 – July 2026
Other flights on this route
Same airports, same journey, different odds of arriving on time.
| Flight | Airline | On time | Median arrival | Operations |
|---|---|---|---|---|
| DL987 | Delta Air Lines | 90.9% | 9 min early | 625 |
| DL849 | Delta Air Lines | 90.8% | 10 min early | 870 |
| DL855 | Delta Air Lines | 87.9% | 8 min early | 1,096 |
| DL862 | Delta Air Lines | 83.8% | 9 min early | 999 |
| DL865 | Delta Air Lines | 78.8% | 7 min early | 1,119 |
| DL350 | Delta Air Lines | 76.3% | 5 min early | 966 |
| DL726 | Delta Air Lines | 74.1% | 5 min early | 1,096 |
| DL300 | Delta Air Lines | 72.0% | 3 min early | 1,050 |
| DL518 this flight | Delta Air Lines | 69.2% | 1 min early | 896 |
Every departure listed carries at least 600 operations, so the comparison is between figures that mean something. DL518 is placed in the same ordering rather than left out of it; the rows around it are the most punctual departures on the route, not all of them, so this is a comparison and not a rank. Schedules change; confirm the departure still operates before booking around this.
Data and methodology
Calculated by FlyerIntel from 896 records of DL518 operating ATL → BOS, published by the US DOT Bureau of Transportation Statistics. A flight counts as delayed when it arrives 15 or more minutes after schedule. Cancelled and diverted flights are excluded from the on-time rate and reported separately. Flight numbers are resolved as carrier plus number plus route, because the same number serves different routes over time.
Full methodology · Data sources · Report a problem
Related research: Most and Least Reliable Flight Numbers · The Delay You Inherit · Making Up Time in the Air
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