Flight profile · Delta Air Lines
DL1239
Seattle (SEA) to Salt Lake City (SLC) · scheduled 7:30 PM – 10:15 PM
How DL1239 performs
602 operations, June 2024 – August 2026.
Between its first and last recorded date on SEA → SLC, DL1239 averaged about 5 operations a week (602 in 815 days, cancelled ones included).
DL1239 arrived on time 82.5% of the time, level with the 83.2% for all SEA → SLC flights: on arrival punctuality it is a typical departure on this route, neither better nor worse.
Source: US DOT Bureau of Transportation Statistics · 602 operations, June 2024 – August 2026 · If DL1239 is cancelled or significantly changed, DOT’s automatic refund rule may entitle you to your money back. The refund checker walks through eligibility.
Where DL1239 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 |
|---|---|---|---|---|---|
| DL1239 | 82.5% | 0.17% | -8 min | 5.3% | 602 |
| Delta Air Lines on SEA → SLC | 87.6% | 0.37% | -9 min | 3.4% | 7,026 |
| All SEA → SLC flights | 83.2% | 0.64% | -6 min | 3.9% | 12,727 |
DL1239 cancelled 1 of 602 operations (0.17%), close to the 0.64% for SEA → SLC.
Source: FlyerIntel analysis of US DOT BTS data · June 2024 – August 2026
Why DL1239 runs late
Where US DOT attributed the delay minutes on this flight.
crew, maintenance, boarding and fueling, all within the carrier’s control
the inbound aircraft was late, so this flight started late
airspace and airport capacity, including weather-driven flow control
weather severe enough to stop this flight specifically
Share of the delay minutes US DOT attributed to each cause for DL1239 on SEA → SLC. Only delays of 15 minutes or more are attributed. What the five causes mean
Source: US DOT Bureau of Transportation Statistics · Data covering June 2024 – August 2026
Does a late aircraft delay this flight?
How often the plane that flies DL1239 comes in late, and what that does to the departure.
The aircraft flying DL1239 came in 15 or more minutes late on 16% 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.
Matched by tail number to the aircraft’s previous flight into SEA: 591 of 601 departures. Unknown, cancelled or diverted inbounds and gaps over 12 hours are left out.
Against the network at the same turn length
| Share of departures | Inbound landed 15+ late |
|---|---|
| DL1239 | 16% |
| Network, same turn | 17% |
67 scheduled minutes is enough to clean and board when the aircraft is on time, with little to spare when it is not.
The network row is every flight with a scheduled turn of 60 to 89 minutes. How often DL1239’s aircraft landed 15 or more minutes late is about the same as the network’s. There are not enough departures in both groups to compare how it left.
Source: US DOT Bureau of Transportation Statistics · Data covering June 2024 – August 2026
From pushback to gate
When it leaves SEA late, does that still matter by the time it reaches SLC?
DL1239 pushes back an average of 9.3 minutes late and reaches the gate at SLC an average of 1.1 minutes late. The 8.2 minutes between those two figures are slack the published schedule already carries, so a late pushback is partly, not fully, made up before the gate. It spends 19.3 minutes on the taxiways at SEA, 1.3 minutes shorter than a typical SEA departure in the same hour.
On arrival at SLC, DL1239 spends 6.9 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 SLC spends on the ground before reaching the gate.
Taxi-out is gate to wheels up and sits inside the scheduled block; the hourly comparison is 30,675 SEA departures. Taxi-in is landing to gate, set against 365,173 arrivals at SLC. More on taxi time.
Source: FlyerIntel analysis of US DOT BTS data · June 2024 – August 2026
The hour it leaves SEA
DL1239 has one departure time, 7:30 PM, so this is what that hour at SEA is worth.
On-time arrival rate. 30,675 departures from SEA are scheduled in the 7 PM–8 PM hour over the period, against 526,113 across the whole day.
DL1239 is scheduled out of SEA at 7:30 PM, in the 7 PM–8 PM bank. Departures from SEA in that hour arrive on time 77.2% of the time against 78.9% across the airport’s whole day, so the hour DL1239 leaves in is an ordinary one for SEA and explains nothing about its record either way.
Both airport figures cover every destination from SEA, so they describe the slot, not this journey; the route comparison is above. Why the hour matters.
Source: FlyerIntel analysis of US DOT BTS data · June 2024 – August 2026 · Hours below 120 departures are not scored.
Other routes DL1239 has flown
Carriers reassign flight numbers. DL1239 also served these 5 other city pairs in the period.
| Route | Operated | Flights | On time |
|---|---|---|---|
| ATL→JFK Atlanta to New York | July 1, 2023 – June 6, 2024 | 199 | 80.1% |
| IAH→LGA Houston to New York | April 9, 2024 – May 6, 2024 | 28 | — |
| LGA→IAH New York to Houston | March 10, 2024 – April 8, 2024 | 30 | — |
| IAH→SLC Houston to Salt Lake City | January 8, 2024 – March 9, 2024 | 52 | — |
| SLC→IAH Salt Lake City to Houston | January 9, 2024 – March 8, 2024 | 35 | — |
The figures above describe only SEA → SLC, the route DL1239 flies now.
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 8 min early
Percentiles over 602 operations; cancelled and diverted flights are counted separately.
Source: US DOT Bureau of Transportation Statistics · Data covering June 2024 – August 2026
Other flights on this route
Same airports, same journey, different odds of arriving on time.
| Flight | Airline | On time | Median arrival | Operations |
|---|---|---|---|---|
| DL1128 | Delta Air Lines | 93.0% | 15 min early | 880 |
| DL1016 | Delta Air Lines | 90.8% | 13 min early | 788 |
| AS630 | Alaska Airlines | 85.2% | 7 min early | 641 |
| DL1120 | Delta Air Lines | 84.6% | 8 min early | 816 |
| DL1239 this flight | Delta Air Lines | 82.5% | 8 min early | 602 |
| DL1165 | Delta Air Lines | 80.4% | 3 min early | 752 |
Among all 6 departures on this route with at least 600 operations, DL1239 has the 5th highest on-time rate, 10.5 points behind the best. Every departure here has at least 600 operations; the other rows are the most punctual on the route, not all of them.
Data and methodology
Calculated by FlyerIntel from 602 records of DL1239 operating SEA → SLC, 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 reported separately, not in the on-time rate.
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