Flight number record
OO 4109
SkyWest Airlines · Atlanta to South Bend
- Route
- ATL → SBN
- Departs
- 19:42
- Flights
- 255
- Period
- September 2025 to August 2026
Historical statistics for September 2025 to August 2026, not live status. For today’s OO 4109, check with SkyWest Airlines. SkyWest Airlines flies under contract for larger airlines, so a ticket for this flight may show a different airline code and number.
OO 4109 draws a D. Roughly one flight in two arrives at least 15 minutes late, and the typical late arrival is close to two hours behind schedule. Build slack into anything you connect to. That rests on 255 flights, with a median arrival 4 minutes late.
The national on-time rate over the same period is 77.3%, so OO 4109 runs 18 points behind the country as a whole. Across a thousand flights that is about 179 extra late arrivals.
Key figures
On time
59.4%
Arrivals under 15 minutes late, of 249 completed flights
Avg delay
110 min
Across delayed arrivals only, not all flights
Cancelled
1.96%
National rate is 1.89%
1 hour+ late
22.5%
National rate is 8.3%
These figures cover 255 flights between September 2025 and August 2026. Beyond the headline rate, 22.5% of arrivals land a full hour or more behind schedule, against 8.3% nationally.
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Schedule
When OO 4109 flies
OO 4109 flies ATL to SBN without a single fixed slot. Its most common scheduled departure was 19:42, used on 61 of 255 flights, with 19:43 (55 flights) and 19:52 (38 flights) next.
- Departs 19:4261 flights23.9%
- Departs 19:4355 flights21.6%
- Departs 19:5238 flights14.9%
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 19:42 departure sits in the 5pm–8pm window. Across every US flight scheduled in that window the on-time rate is 68.0%, and OO 4109 runs 9 points worse at 59.4%. 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
OO 4109 next to ATL to SBN
Every carrier on ATL to SBN combined arrived on time 74.5% of the time across 1,030 flights, so OO 4109 is 15 points behind it. SkyWest flew 1,029 flights on the same city pair under all its flight numbers, including this one, and those ran 74.4% on time. Across its whole network SkyWest Airlines managed 78.7%, which this flight trails by 19 points.
| Compared with | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| OO 4109thin sample | 255 | 59.4% | 110 min | 1.96% | D |
| All SkyWest Airlines on ATL–SBN | 1,029 | 74.4% | 106 min | 2.04% | C |
| All carriers on ATL–SBN | 1,030 | 74.5% | 106 min | 2.04% | C |
| SkyWest Airlines, whole network | 855,406 | 78.7% | 88 min | 1.79% | B |
Across the year
OO 4109 quarter by quarter
OO 4109 did not run the same all year. Its best quarter was Apr–Jun 2026 at 68.9% on time and its weakest Jan–Mar 2026 at 52.9%, a swing of 16 points on roughly 85 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.
- Oct–Dec 202512 flights—
- Jan–Mar 202690 flights52.9%
- Apr–Jun 202691 flights68.9%
- Jul–Sep 202662 flights56.5%
Scale runs 45% to 75%. Rows with fewer than 30 flights show a dash.
By weekday, OO 4109 did best on Wednesday at 71.4% on time and worst on Monday at 45.9%. Each day rests on about 36 flights, so a gap of 26 points is worth noticing but could still narrow in another year.
Arrival by arrival
How late OO 4109 runs when it is late
When OO 4109 is late it tends to be very late: 56 of its 101 late arrivals were an hour or more behind, and 24 were two hours or more.
- 15+ min early39 flights15.7%
- Within 15 min109 flights43.8%
- 15–29 min late25 flights10.0%
- 30–59 min late20 flights8.0%
- 1–2 hours late32 flights12.9%
- 2+ hours late24 flights9.6%
Scale runs 0% to 100%.
Share of 249 completed flights by arrival against schedule.
Time lost at the gate mostly stays lost. Of 91 departures that left 15 minutes late or more, only 7 made it up before arrival. In the other direction, 17 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 SBN.
The worst days
Worst days for OO 4109
The latest arrival of the period was on 4 May 2026, 14 hours 53 minutes behind schedule; most of its delay minutes were filed as carrier-caused (crew, maintenance, fuelling, baggage). The same cause led on four of the five worst days.
| Date | Arrived late by | Largest filed cause |
|---|---|---|
| 4 May 2026 | 14 hours 53 minutes | Carrier |
| 13 January 2026 | 14 hours 47 minutes | Carrier |
| 26 January 2026 | 14 hours 43 minutes | Carrier |
| 24 June 2026 | 13 hours 3 minutes | Carrier |
| 6 May 2026 | 5 hours 21 minutes | Extreme weather |
Delay causes
Why OO 4109 runs late
Carrier accounts for 69% of the 11,000 delay minutes carriers reported here, and the remaining four split what is left.
- 69%Carrier
- 19%Extreme weather
- 12%National Airspace System
Extreme weather accounts for 19% of delay minutes, well above the single-digit share typical across the system. Weather delays are lumpy: they arrive as whole bad days rather than as a steady drag, so the quarterly figures above are the more useful view of the risk. The national share is 6%, so this operation carries roughly 3.2 times the usual weather exposure. The split is drawn from 11,059 delay minutes reported on OO 4109.
Cancellations sit at 1.96% against a national 1.89%, which is ordinary. Diversions add another 0.39%.
Connections and routes
What a delay on this flight costs
22.5% 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 566 miles between these two airports put this in the middle of the US network, around two and a half to three hours of block time. That is enough cruise to absorb a ten-minute late pushback and not enough to absorb thirty.
The same number turns up on two other city pairs in the data, including MSP to MOT (89) and PIT to DTW (9), but none flew often enough under OO 4109 to report a rate for. Carriers move flight numbers between routes, so the figures on this page apply to ATL to SBN only.
One caution: this is a thin sample. 255 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 OO 4109
For a booking, OO 4109 is a flight to put a long connection behind. 22.5% of its completed flights arrived an hour or more late, which a short layover will not absorb. If the onward flight is on a separate ticket, the risk sits with you.
Related
Where to go next
- ATL to SBN, every carrier and departure
- SBN to ATL, the return direction
- SkyWest Airlines 4033 on the same route75.1%
- Hartsfield-Jackson Atlanta International (ATL) delay statistics
- SkyWest Airlines on-time record
- Every SkyWest Airlines flight number with a record
- The most and least reliable flight numbers in the US
- How often a connection fails at the major US hubs
A flight number here means SkyWest Airlines’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.