Flight number record
YX 3551
Republic Airways · Chicago to Louisville
- Route
- ORD → SDF
- Departs
- 19:52
- Flights
- 275
- Period
- September 2025 to August 2026
Historical statistics for September 2025 to August 2026, not live status. For today’s YX 3551, check with Republic Airways. Republic Airways flies under contract for larger airlines, so a ticket for this flight may show a different airline code and number.
YX 3551 lands a B, about a point worse than the national rate of 77.3%. About one flight in four arrives 15 minutes late or worse, and those flights are late by a little over an hour on average. That rests on 275 flights, with a median arrival 8 minutes early.
Key figures
On time
76.1%
Arrivals under 15 minutes late, of 268 completed flights
Avg delay
79 min
Across delayed arrivals only, not all flights
Cancelled
2.55%
National rate is 1.89%
1 hour+ late
9.0%
National rate is 8.3%
These figures cover 275 flights between September 2025 and August 2026. Beyond the headline rate, 9.0% of arrivals land a full hour or more behind schedule, against 8.3% nationally.
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Schedule
When YX 3551 flies
YX 3551 flies ORD to SDF without a single fixed slot. Its most common scheduled departure was 19:52, used on 56 of 275 flights, with 19:55 (52 flights) and 19:40 (45 flights) next.
- Departs 19:5256 flights20.4%
- Departs 19:5552 flights18.9%
- Departs 19:4045 flights16.4%
Scale runs 0% to 100%.
Share of scheduled departures at each local time. Times used on fewer than one flight in ten are not listed.
A 19:52 departure sits in the 5pm–8pm window. Across every US flight scheduled in that window the on-time rate is 68.0%, and YX 3551 runs 8 points better at 76.1%. By that time of day most aircraft have flown several legs already, and whatever went wrong earlier is still in the schedule.
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Against the route
YX 3551 next to ORD to SDF
Every carrier on ORD to SDF combined arrived on time 75.8% of the time across 2,792 flights, so YX 3551 is about level with it. Republic flew 1,850 flights on the same city pair under all its flight numbers, including this one, and those ran 75.8% on time. Across its whole network Republic Airways managed 78.1%, which this flight trails by 2 points.
| Compared with | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| YX 3551thin sample | 275 | 76.1% | 79 min | 2.55% | B |
| All Republic Airways on ORD–SDF | 1,850 | 75.8% | 77 min | 4.11% | B− |
| All carriers on ORD–SDF | 2,792 | 75.8% | 71 min | 3.58% | B− |
| Republic Airways, whole network | 364,452 | 78.1% | 74 min | 4.55% | B− |
Across the year
YX 3551 quarter by quarter
YX 3551 did not run the same all year. Its best quarter was Jul–Sep 2025 at 90.0% on time and its weakest Jan–Mar 2026 at 71.6%, a swing of 18 points on roughly 69 flights a quarter. The twelve-month rate averages over that, so if you are flying in a weak quarter the quarter's own figure is the better guide.
- Jul–Sep 202530 flights90.0%
- Oct–Dec 202591 flights74.2%
- Jan–Mar 202690 flights71.6%
- Apr–Jun 202646 flights81.8%
- Jul–Sep 202618 flights—
Scale runs 65% to 95%. Rows with fewer than 30 flights show a dash.
By weekday, YX 3551 did best on Friday at 89.2% on time and worst on Monday at 66.7%. Each day rests on about 39 flights, so a gap of 23 points is worth noticing but could still narrow in another year.
Arrival by arrival
How late YX 3551 runs when it is late
YX 3551 often beats the schedule: 94 of 268 completed flights, 35%, arrived 15 minutes or more early. The 64 late arrivals split 16 under half an hour, 24 between 30 and 60 minutes, and 24 an hour or more.
- 15+ min early94 flights35.1%
- Within 15 min110 flights41.0%
- 15–29 min late16 flights6.0%
- 30–59 min late24 flights9.0%
- 1–2 hours late14 flights5.2%
- 2+ hours late10 flights3.7%
Scale runs 0% to 100%.
Share of 268 completed flights by arrival against schedule.
9 of 49 late departures made up the time and arrived on time, 18% of them. In the other direction, 24 flights left on time yet arrived 15 minutes late or more, so that delay built up after pushback: in the air, in a holding pattern or on the ground at SDF.
The worst days
Worst days for YX 3551
The latest arrival of the period was on 30 November 2025, 13 hours 43 minutes behind schedule; most of its delay minutes were filed as carrier-caused (crew, maintenance, fuelling, baggage). On four of the five worst days the largest share was filed as a late-arriving aircraft.
| Date | Arrived late by | Largest filed cause |
|---|---|---|
| 30 November 2025 | 13 hours 43 minutes | Carrier |
| 26 March 2026 | 5 hours 37 minutes | Late-arriving aircraft |
| 30 December 2025 | 5 hours 1 minute | Late-arriving aircraft |
| 13 April 2026 | 3 hours 45 minutes | Late-arriving aircraft |
| 12 March 2026 | 3 hours 32 minutes | Late-arriving aircraft |
Delay causes
Why YX 3551 runs late
Late-arriving aircraft accounts for 56% of the 5,052 delay minutes carriers reported here, and the remaining four split what is left.
- 56%Late-arriving aircraft
- 22%National Airspace System
- 21%Carrier
- 1%Extreme weather
56% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 5,052 reported delay minutes here, that single category outweighs weather by 45 to one. The split is drawn from 5,052 delay minutes reported on YX 3551.
Cancellations run at 2.55%, against 1.89% nationally. That is about one flight in 40 cancelled outright. A cancelled flight is invisible in every on-time figure on this page, so the punctuality numbers above describe only the flights that actually operated.
Connections and routes
What a delay on this flight costs
9.0% of arrivals land a full hour or more behind schedule, against 8.3% nationally. Ninety minutes is the honest minimum for a connection here, and two hours if the onward flight is on a separate ticket.
The same number turns up on six other city pairs in the data, including PWM to ORD (56), IND to EWR (24) and XNA to ORD (18), but none flew often enough under YX 3551 to report a rate for. Carriers move flight numbers between routes, so the figures on this page apply to ORD to SDF only.
One caution: this is a thin sample. 275 flights over twelve months is enough to clear this site's floor but not enough to pin the rate down tightly, and a single bad week moves it by more than a point. Treat the grade as a rough reading.
What to do with this
Booking YX 3551
For a booking, the cancellation rate is the figure to plan around on YX 3551: 2.55% of its 275 scheduled flights did not operate. A late arrival costs a little over an hour, but a cancellation costs the day, so leave a later option open.
Related
Where to go next
- ORD to SDF, every carrier and departure
- SDF to ORD, the return direction
- Republic Airways 3598 on the same route74.2%
- Republic Airways 4603 on the same route75.3%
- Chicago O'Hare International (ORD) delay statistics
- Republic Airways on-time record
- Every Republic Airways flight number with a record
- The most and least reliable flight numbers in the US
- Why the first flight of the morning is statistically safest
A flight number here means Republic Airways’s own number as it reports to the DOT. How the figures are computed is on the methodology page.
Source: US DOT Bureau of Transportation Statistics, on-time performance data, September 2025 to August 2026. Last updated ; recomputed monthly. How this data is collected.