Flight profile · Delta Air Lines
DL1780
Boston (BOS) to San Juan (SJU) · scheduled 8:10 AM – 12:15 PM
How DL1780 performs
1,127 operations, July 2023 – July 2026.
DL1780 arrived on time 80.2% of the time, against 67.7% for all BOS → SJU flights, so this departure is 12.5 percentage points better than the route as a whole.
Source: US DOT Bureau of Transportation Statistics · 1,127 operations, July 2023 – July 2026 · If DL1780 is cancelled or significantly changed, DOT’s automatic refund rule may entitle you to your money back. The refund checker walks through eligibility.
What stands out
How DL1780 compares to other flight numbers, not just to itself.
This flight runs unusually far ahead of the BOS → SJU route as a whole, better than 95% of 11,788 comparable flight numbers.
80.2% on time for this specific departure, against 67.7% for every BOS → SJU flight.
Source: FlyerIntel analysis of US DOT BTS data · July 2023 – July 2026 · The one thing about this specific departure that ranks most extreme against every other published flight number, out of everything FlyerIntel checks — shown only when something clears a real statistical bar, not for every flight.
Where DL1780 is right now
A live reading, only if you ask for it. It is not part of the reliability record above.
Ask for the position of DL1780 right now, if receivers on the ground are hearing it. Nothing is requested until you press the button.
Against the rest of the route
| Flight or route | On time | Cancelled | Median delay | Severe | Flights |
|---|---|---|---|---|---|
| DL1780 | 80.2% | 0.44% | -7 min | 4.5% | 1,127 |
| Delta Air Lines on BOS → SJU | 79.3% | 0.66% | -7 min | 5.1% | 1,207 |
| All BOS → SJU flights | 67.7% | 1.70% | 0 min | 12.3% | 5,995 |
DL1780 has cancelled 0.44% of its scheduled departures (5 of 1,127), against 1.70% for all BOS → SJU flights — this specific departure cancels 1.3 percentage points less often than the route as a whole. Different flight numbers on the same route can carry different aircraft, crews and schedules, so this is a fact about DL1780 specifically, not about the route it flies.
Source: FlyerIntel analysis of US DOT BTS data · July 2023 – July 2026
Why DL1780 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
Share of the delay minutes US DOT attributed to each cause for DL1780 on BOS → SJU. 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 DL1780 comes in late, and what that does to the departure.
When the aircraft came in 15 or more minutes late, DL1780 pushed back an average of 26 minutes late; when it came in on time or early, an average of 4 minutes late.
Each departure is matched to the flight the same aircraft flew into BOS just before it, using the tail number in the DOT file, 1,025 of 1,122 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 |
|---|---|---|---|
| DL1780 | 14% | 55% | 11% |
| 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 DL1780’s aircraft landed 15 or more minutes late is lower than the network’s and, once the aircraft was late, how often DL1780 left 15 or more minutes late is lower than 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 BOS late, does that still matter by the time it reaches SJU?
DL1780 pushes back an average of 7.5 minutes late and reaches the gate at SJU an average of 0.9 minutes late. The 6.6 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. It spends 24.5 minutes on the taxiways at BOS, 2.5 minutes longer than a typical BOS departure in the same hour.
On arrival at SJU, DL1780 spends 5.8 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 about what any arrival at SJU spends on the ground before reaching the gate.
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 SJU. Taxi-out is gate to wheels up and sits inside the scheduled block rather than on top of it; the comparison is 35,349 departures from BOS scheduled in the clock hour DL1780 most often leaves in. Taxi-in is landing to gate, compared against every arrival FlyerIntel has on file at SJU (109,607 flights), not just DL1780’s own. More on taxi time.
Source: FlyerIntel analysis of US DOT BTS data · July 2023 – July 2026
The hour it leaves BOS
Part of any flight’s record belongs to the clock rather than to the flight. DL1780 has one departure time, so this is what that time is worth.
On-time arrival rate. 35,349 departures from BOS are scheduled in the 8 AM–9 AM hour over the period, against 440,893 across the whole day.
DL1780 is scheduled out of BOS at 8:10 AM, in the 8 AM–9 AM bank. Departures from BOS in that hour arrive on time 84.8% of the time against 77.2% across the airport’s whole day — the slot alone is worth 7.6 points better before anything about this particular flight is considered.
The two airport figures cover every departure from BOS 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 DL1780 run worse on particular days?
Saturday is historically the most reliable day and Tuesday the least, a gap of 5.5 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 DL1780 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 |
|---|---|---|---|
| SJU→BOS San Juan to Boston | July 1, 2023 – July 31, 2026 | 1,048 | 84.1% |
Because the same number has served different journeys, the statistics above describe only the route DL1780 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.
32 min late
against a median of 7 min early
Percentiles over 1,127 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 |
|---|---|---|---|---|
| DL1780 this flight | Delta Air Lines | 80.2% | 7 min early | 1,127 |
| B6861 | JetBlue | 72.7% | 3 min early | 1,033 |
| B6561 | JetBlue | 63.3% | 3 min late | 959 |
Every departure listed carries at least 600 operations, so the comparison is between figures that mean something. DL1780 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 1,127 records of DL1780 operating BOS → SJU, 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
Analysis last recomputed