Flight profile · Delta Air Lines
DL1223
Atlanta (ATL) to Houston (IAH) · scheduled 4:25 PM – 5:38 PM
How DL1223 performs
740 operations, September 2023 – July 2026.
DL1223 arrived on time 73.6% of the time, against 75.4% for all ATL → IAH flights, so this departure is 1.8 percentage points worse than the route as a whole. Against Delta Air Lines’ own flights on this route it is 2.5 points worse.
Source: US DOT Bureau of Transportation Statistics · 740 operations, September 2023 – July 2026 · If DL1223 is cancelled or significantly changed, DOT’s automatic refund rule may entitle you to your money back. The refund checker walks through eligibility.
Where DL1223 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 |
|---|---|---|---|---|---|
| DL1223 | 73.6% | 1.08% | 0 min | 8.1% | 740 |
| Delta Air Lines on ATL → IAH | 76.1% | 1.49% | -2 min | 7.3% | 7,359 |
| All ATL → IAH flights | 75.4% | 1.66% | -3 min | 8.9% | 14,365 |
Source: FlyerIntel analysis of US DOT BTS data · September 2023 – July 2026
Why DL1223 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 DL1223 on ATL → IAH. Only delays of 15 minutes or more are attributed.
Source: US DOT Bureau of Transportation Statistics · Data covering September 2023 – July 2026
Does a late aircraft delay this flight?
How often the plane that flies DL1223 comes in late, and what that does to the departure.
The aircraft flying DL1223 came in 15 or more minutes late on 15% 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 ATL just before it, using the tail number in the DOT file, 687 of 732 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 |
|---|---|
| DL1223 | 15% |
| 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 DL1223’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.
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 September 2023 – July 2026
From pushback to gate
When it leaves ATL late, does that still matter by the time it reaches IAH?
DL1223 pushes back an average of 13.9 minutes late and reaches the gate at IAH an average of 11.4 minutes late. The 2.5 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 15.4 minutes on the taxiways at ATL, 1.6 minutes shorter than a typical ATL departure in the same hour.
On arrival at IAH, DL1223 spends 10.2 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 IAH 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 IAH. Taxi-out is gate to wheels up and sits inside the scheduled block rather than on top of it; the comparison is 60,834 departures from ATL scheduled in the clock hour DL1223 most often leaves in. Taxi-in is landing to gate, compared against every arrival FlyerIntel has on file at IAH (359,471 flights), not just DL1223’s own. More on taxi time.
Source: FlyerIntel analysis of US DOT BTS data · September 2023 – July 2026
The hour it leaves ATL
Part of any flight’s record belongs to the clock rather than to the flight. DL1223 has one departure time, so this is what that time is worth.
On-time arrival rate. 60,834 departures from ATL are scheduled in the 4 PM–5 PM hour over the period, against 1,012,247 across the whole day.
DL1223 is scheduled out of ATL at 4:25 PM, in the 4 PM–5 PM bank. Departures from ATL in that hour arrive on time 73.3% of the time against 78.7% across the airport’s whole day — the slot alone is worth 5.4 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 · September 2023 – July 2026 · Hours below 120 departures are not scored.
Other routes DL1223 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 |
|---|---|---|---|
| IAH→ATL Houston to Atlanta | September 10, 2023 – July 31, 2026 | 677 | 75.9% |
| SEA→GEG Seattle to Spokane | March 8, 2026 – April 12, 2026 | 36 | — |
| RSW→BOS Fort Myers to Boston | June 8, 2025 – December 19, 2025 | 195 | 79.9% |
| PSP→MSP Palm Springs to Minneapolis | December 22, 2023 – January 7, 2024 | 17 | — |
| ATL→BTR Atlanta to Baton Rouge | November 2–3, 2023 | 2 | — |
| BTR→ATL Baton Rouge to Atlanta | November 2–3, 2023 | 2 | — |
| LGA→IAH New York to Houston | July 15, 2023 – September 4, 2023 | 10 | — |
| RDU→LAX Raleigh–Durham to Los Angeles | July 10–31, 2023 | 13 | — |
| BDL→MSP Hartford to Minneapolis | July 1–8, 2023 | 7 | — |
| MSP→BDL Minneapolis to Hartford | July 1–8, 2023 | 7 | — |
Because the same number has served different journeys, the statistics above describe only the route DL1223 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.
48 min late
against a median of 0 min early
Percentiles over 740 operations; cancelled and diverted flights are counted separately.
Source: US DOT Bureau of Transportation Statistics · Data covering September 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 |
|---|---|---|---|---|
| DL1585 | Delta Air Lines | 84.9% | 4 min early | 942 |
| DL1682 | Delta Air Lines | 82.8% | 6 min early | 991 |
| DL1572 | Delta Air Lines | 80.1% | 4 min early | 869 |
| F91403 | Frontier Airlines | 75.4% | 7 min early | 712 |
| DL1223 this flight | Delta Air Lines | 73.6% | 0 min early | 740 |
| DL1601 | Delta Air Lines | 71.6% | 0 min early | 1,119 |
| DL1284 | Delta Air Lines | 71.3% | 0 min early | 998 |
Every departure listed carries at least 600 operations, so the comparison is between figures that mean something. DL1223 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 740 records of DL1223 operating ATL → IAH, 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