Flight profile · Delta Air Lines
DL1421
San Francisco (SFO) to Los Angeles (LAX) · scheduled 8:55 AM – 10:32 AM
How DL1421 performs
830 operations, July 2023 – July 2026.
DL1421 arrived on time 90.1% of the time, against 77.1% for all SFO → LAX flights, so this departure is 13.0 percentage points better than the route as a whole. Against Delta Air Lines’ own flights on this route it is 11.3 points better.
DL1421’s scheduled departure has moved during the period FlyerIntel has on file: it typically left around 9:30 AM earlier on, and around 9:00 AM more recently — a 30-minute shift, not the few minutes of day-to-day rounding every published schedule carries. Confirm the current departure time before booking around an older listing.
Source: US DOT Bureau of Transportation Statistics · 830 operations, July 2023 – July 2026 · If DL1421 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 DL1421 compares to other flight numbers, not just to itself.
This flight runs unusually far ahead of the SFO → LAX route as a whole, better than 95% of 11,788 comparable flight numbers.
90.1% on time for this specific departure, against 77.1% for every SFO → LAX 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 DL1421 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 |
|---|---|---|---|---|---|
| DL1421 | 90.1% | 1.69% | -14 min | 3.9% | 830 |
| Delta Air Lines on SFO → LAX | 78.8% | 0.84% | -10 min | 7.6% | 7,251 |
| All SFO → LAX flights | 77.1% | 0.70% | -5 min | 7.4% | 34,804 |
Source: FlyerIntel analysis of US DOT BTS data · July 2023 – July 2026
Why DL1421 runs late
Where US DOT attributed the delay minutes on this flight.
the inbound aircraft was late, so this flight started late
crew, maintenance, boarding and fueling, all within the carrier’s control
weather severe enough to stop this flight specifically
airspace and airport capacity, including weather-driven flow control
screening or terminal security incidents
Share of the delay minutes US DOT attributed to each cause for DL1421 on SFO → LAX. 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 DL1421 comes in late, and what that does to the departure.
The aircraft flying DL1421 came in 15 or more minutes late on 8% of the departures where its previous flight is known. There are not enough departures in both groups to say how the flight left after a late one and after an on-time one.
Each departure is matched to the flight the same aircraft flew into SFO just before it, using the tail number in the DOT file, 799 of 816 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 |
|---|---|
| DL1421 | 8% |
| Network, same turn | 17% |
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 DL1421’s aircraft landed 15 or more minutes late is lower than the network’s. There are not enough departures in both groups to compare how it left.
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 SFO late, does that still matter by the time it reaches LAX?
DL1421 pushes back an average of 4.2 minutes late and reaches the gate at LAX an average of 4.3 minutes early. The 8.5 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 19.4 minutes on the taxiways at SFO, 3.6 minutes shorter than a typical SFO departure in the same hour.
On arrival at LAX, DL1421 spends 10.9 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 LAX 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 LAX. Taxi-out is gate to wheels up and sits inside the scheduled block rather than on top of it; the comparison is 38,724 departures from SFO scheduled in the clock hour DL1421 most often leaves in. Taxi-in is landing to gate, compared against every arrival FlyerIntel has on file at LAX (595,170 flights), not just DL1421’s own. More on taxi time.
Source: FlyerIntel analysis of US DOT BTS data · July 2023 – July 2026
The hour it leaves SFO
Part of any flight’s record belongs to the clock rather than to the flight. DL1421 has one departure time, so this is what that time is worth.
On-time arrival rate. 38,724 departures from SFO are scheduled in the 8 AM–9 AM hour over the period, against 435,779 across the whole day.
DL1421 is scheduled out of SFO at 8:55 AM, in the 8 AM–9 AM bank. Departures from SFO in that hour arrive on time 85.2% of the time against 78.7% across the airport’s whole day — the slot alone is worth 6.5 points better before anything about this particular flight is considered.
The two airport figures cover every departure from SFO 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 DL1421 run worse on particular days?
Monday is historically the most reliable day and Friday the least, a gap of 7.6 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 DL1421 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 |
|---|---|---|---|
| LAX→SFO Los Angeles to San Francisco | July 9, 2023 – July 31, 2026 | 825 | 91.9% |
| PIT→MSP Pittsburgh to Minneapolis | May 7, 2024 – June 6, 2024 | 31 | — |
| LGA→DTW New York to Detroit | April 9, 2024 – May 6, 2024 | 28 | — |
| MDW→ATL Chicago to Atlanta | January 8, 2024 – March 9, 2024 | 62 | — |
| BNA→ATL Nashville to Atlanta | December 16, 2023 – January 7, 2024 | 23 | — |
| BOI→SLC Boise to Salt Lake City | September 5, 2023 – December 15, 2023 | 102 | 94.1% |
| SLC→BOI Salt Lake City to Boise | September 5, 2023 – December 15, 2023 | 102 | 96.1% |
Because the same number has served different journeys, the statistics above describe only the route DL1421 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.
13 min late
against a median of 14 min early
Percentiles over 830 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 |
|---|---|---|---|---|
| DL1598 | Delta Air Lines | 94.9% | 15 min early | 776 |
| DL1421 this flight | Delta Air Lines | 90.1% | 14 min early | 830 |
| UA1754 | United Airlines | 75.6% | 2 min early | 607 |
| DL2272 | Delta Air Lines | 74.8% | 7 min early | 894 |
| DL1715 | Delta Air Lines | 69.6% | 2 min early | 695 |
| DL2267 | Delta Air Lines | 67.8% | 4 min early | 897 |
Every departure listed carries at least 600 operations, so the comparison is between figures that mean something. DL1421 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 830 records of DL1421 operating SFO → LAX, 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