FlyerIntel Research
Most and Least Reliable Flight Numbers
Two flights can leave the same airport for the same city on the same day and arrive on time at wildly different rates. The number on the ticket is not decoration.
Published August 30, 2026 · Source period July 2023 – July 2026
Summary
Across 5,504 scheduled flight numbers with at least 400 operations each, OO4235 (SGU to SLC) arrives on time 97.9% of the time, while OO5961 (SMF to SFO) manages 43.4%, a spread of 54.4 percentage points between two flights sold the same way. The median flight number sits at 80.0%. A specific departure is a far better predictor of arriving on time than the airline operating it.
Key findings
- OO4235 SGU → SLC is the most reliable regular departure in the dataset at 97.9% on time across 1,123 operations.
- OO5961 SMF → SFO is the least reliable at 43.4%.
- The gap between them is 54.4 points; the median flight number arrives on time 80.0% of the time.
- Short flights from uncongested airports dominate the top of the table, and long flights into congested hubs late in the day dominate the bottom.
Why a flight number has a personality
A flight number is a fixed slot in an airline’s daily plan: a scheduled departure time, a position in an aircraft’s sequence of legs, a crew pairing, a gate, and a place in the queue at both ends. All of those repeat, day after day, which is why the same number can be dependably early for years while another number on the identical route is dependably late. Booking sites show you the price and the times. They do not show you that one of these two departures arrives on time nine times in ten and the other barely one time in two.
The 25 most reliable flight numbers
| Flight | Airline | Route | On time | Median arrival | Operations |
|---|---|---|---|---|---|
| OO4235 | SkyWest Airlines | SGU → SLC | 97.9% | 14 min early | 1,123 |
| OO3745 | SkyWest Airlines | TUS → SLC | 97.6% | 18 min early | 785 |
| OO4061 | SkyWest Airlines | OAK → SLC | 96.9% | 14 min early | 419 |
| DL886 | Delta Air Lines | TUS → ATL | 96.9% | 14 min early | 785 |
| OO4230 | SkyWest Airlines | GJT → SLC | 96.9% | 16 min early | 605 |
| OO4037 | SkyWest Airlines | SUN → SLC | 96.8% | 18 min early | 1,010 |
| DL1535 | Delta Air Lines | PHX → SLC | 96.8% | 13 min early | 785 |
| UA1724 | United Airlines | KOA → SFO | 96.8% | 19 min early | 943 |
| DL3028 | Delta Air Lines | GSP → ATL | 96.7% | 13 min early | 583 |
| DL1270 | Delta Air Lines | PDX → SLC | 96.7% | 12 min early | 785 |
| UA1889 | United Airlines | SMF → DEN | 96.4% | 11 min early | 418 |
| OO4138 | SkyWest Airlines | FAT → SLC | 96.3% | 16 min early | 1,012 |
| OO3985 | SkyWest Airlines | SLC → SUN | 96.3% | 17 min early | 708 |
| OO3803 | SkyWest Airlines | SLC → SBA | 96.3% | 20 min early | 435 |
| DL2369 | Delta Air Lines | PDX → MSP | 96.3% | 14 min early | 779 |
| UA1750 | United Airlines | OGG → SFO | 96.2% | 21 min early | 640 |
| UA459 | United Airlines | PDX → DEN | 96.2% | 14 min early | 798 |
| DL2178 | Delta Air Lines | SFO → MSP | 96.1% | 13 min early | 784 |
| OO4311 | SkyWest Airlines | EKO → SLC | 96.1% | 20 min early | 753 |
| UA1734 | United Airlines | BOS → IAD | 96.1% | 12 min early | 623 |
| AA418 | American Airlines | BOS → CLT | 96.1% | 20 min early | 495 |
| DL3187 | Delta Air Lines | ILM → ATL | 96.1% | 13 min early | 466 |
| OO4030 | SkyWest Airlines | PSP → SLC | 96.0% | 17 min early | 1,012 |
| OO4152 | SkyWest Airlines | ABQ → SLC | 96.0% | 13 min early | 403 |
| DL2674 | Delta Air Lines | LAS → SLC | 96.0% | 11 min early | 1,037 |
The 25 least reliable flight numbers
| Flight | Airline | Route | On time | Median arrival | Operations |
|---|---|---|---|---|---|
| OO5961 | SkyWest Airlines | SMF → SFO | 43.4% | 19 min late | 421 |
| F93216 | Frontier Airlines | LAX → ATL | 45.9% | 18 min late | 610 |
| OO4808 | SkyWest Airlines | PIA → ORD | 45.9% | 17 min late | 423 |
| UA2179 | United Airlines | ORD → SFO | 47.4% | 16 min late | 410 |
| UA254 | United Airlines | EWR → ORD | 47.4% | 17 min late | 732 |
| AA662 | American Airlines | DFW → DEN | 47.6% | 16 min late | 788 |
| F91094 | Frontier Airlines | SFO → DEN | 48.3% | 16 min late | 467 |
| F94602 | Frontier Airlines | ATL → EWR | 48.7% | 16 min late | 626 |
| B6384 | JetBlue | MCO → JFK | 49.1% | 16 min late | 581 |
| F92677 | Frontier Airlines | ONT → SFO | 49.5% | 15 min late | 563 |
| AA1234 | American Airlines | DFW → MKE | 49.7% | 15 min late | 561 |
| F93097 | Frontier Airlines | ATL → DFW | 49.8% | 15 min late | 572 |
| DL727 | Delta Air Lines | ATL → DCA | 50.2% | 14 min late | 544 |
| AA2235 | American Airlines | DFW → DEN | 50.3% | 14 min late | 622 |
| AA2186 | American Airlines | DFW → MCO | 50.4% | 14 min late | 922 |
| AA421 | American Airlines | DFW → SYR | 50.5% | 14 min late | 575 |
| F92509 | Frontier Airlines | BWI → ATL | 50.6% | 13 min late | 438 |
| B6998 | JetBlue | MCO → LGA | 51.1% | 12 min late | 631 |
| AA1322 | American Airlines | DFW → DEN | 51.1% | 14 min late | 1,078 |
| AA398 | American Airlines | DFW → CMH | 51.3% | 14 min late | 477 |
| AA1104 | American Airlines | DFW → BOI | 51.3% | 13 min late | 622 |
| AA509 | American Airlines | DFW → SMF | 51.3% | 13 min late | 428 |
| AA1392 | American Airlines | DFW → IAH | 51.4% | 12 min late | 500 |
| B61284 | JetBlue | MCO → JFK | 51.4% | 13 min late | 629 |
| UA1015 | United Airlines | BOS → ORD | 51.5% | 14 min late | 463 |
How to use this without being misled
Schedules change. An airline can retime a flight, hand it to a different aircraft type, or retire the number entirely, and the history stops describing the future at that moment. These figures cover three years, so a number that was moved recently still carries its old record here. Treat a place in either table as a reason to look at the departure’s own page and check when it flies and how consistent it has been, not as a guarantee about the flight you are about to book.
Pages for what this report covers
Airports: Salt Lake City (SLC) · Sacramento (SMF) · San Francisco (SFO) · Tucson (TUS) · Oakland (OAK) · Atlanta (ATL) · Phoenix (PHX) · Portland (PDX) · Denver (DEN) · Santa Barbara (SBA)
Routes: PHX → SLC · SMF → DEN · PDX → DEN · BOS → CLT · LAS → SLC · LAX → ATL
Airlines: SkyWest Airlines · Delta Air Lines · United Airlines · American Airlines · Frontier Airlines · JetBlue
Methodology
Calculated by FlyerIntel from 21,708,321 individual flight records in the US Department of Transportation Bureau of Transportation Statistics Reporting Carrier On-Time Performance dataset, covering July 2023 through July 2026. Following BTS methodology, a flight counts as delayed when it arrives 15 or more minutes after its scheduled arrival time. Cancelled and diverted flights have no arrival time and are excluded from on-time rates rather than counted as late; cancellation rates are reported separately. Full definitions are published at /methodology/. A flight number is identified by its carrier, its number and its route together, because the same number serves different city pairs over time and the combination is what has a consistent schedule. Only combinations with at least 400 completed operations are ranked, which is well above the site’s ordinary publication threshold and keeps a single unlucky month out of the tables.
Limitations
The source dataset covers scheduled domestic flights operated by carriers above the DOT reporting threshold; smaller carriers and international flights are not included. Flights sold under a mainline brand but flown by a regional carrier are attributed to the operating carrier, which is how the DOT records them. Past performance describes what has happened and is not a prediction about any individual flight. A flight number’s record is a property of its schedule as it stood over the period, not a property of the aircraft or crew you will actually get. Numbers that were retimed or retired during the period carry their historical record here.
Sources
- FlyerIntel analysis — FlyerIntel · source
- Reporting Carrier On-Time Performance — US Department of Transportation, Bureau of Transportation Statistics · source
Full FlyerIntel methodology · Report a problem with this analysis