81% of flights leaving Sun Valley (SUN) arrived on time over the past 12 months, 6 points better than the national average of 76%. About 9 flights leave SUN on a typical day; 1.4% were cancelled. 83% pushed back from the gate on time, so most of the lateness is already there when the flight leaves the gate.
At a glance
- Best hour to fly: 3 p.m. (92% on time). Worst: 2 p.m. (77%).
- Best month: November (96%). Worst: December (78%).
- Most reliable airline here: Delta Air Lines (92%), vs United Airlines at 77%.
- Biggest delay cause: the airlines themselves (38% of delay minutes).
- Year on year: getting worse (83% → 81%).
How late?
The on-time rate treats a flight 20 minutes late the same as one 5 hours late. Here's the split for flights leaving SUN: when a flight was late, it was under 45 minutes late 43% of the time. About 1 in 13 flights landed an hour or more late, and 1 in 41 three hours or more; 1.4% were cancelled outright.
- On time or early81%
- 15–30 min late4.8%
- 30–60 min late4.3%
- 1–2 hours late3.6%
- 2–3 hours late1.6%
- 3+ hours late2.4%
- Diverted0.4%
- Cancelled1.4%
Share of all 3,227 scheduled flights, past 12 months, by arrival time against schedule.
Best time of day to fly out of SUN
Departure time makes a real difference at SUN. Flights scheduled to leave at 3 p.m. arrived on time 92% of the time; at 2 p.m. it was 77%, a 15-point gap. Early planes usually start the day at the airport, so they haven't had a chance to pick up delays elsewhere. By evening a late inbound aircraft, a crew running out of duty hours or an afternoon thunderstorm can push one late flight into the next. Cancellations cluster too: 1 p.m. departures were cancelled 3.1% of the time, against 1.4% overall.
Hour × month
Combine the two and the spread is wider still. The most reliable combination at SUN was a 7 a.m. departure in September (98% on time); the least, 8 a.m. in August (65%). If you can only move one thing, move the hour. Departure hour usually shifts the odds more than the month does.
Each cell: on-time rate for that departure hour in that calendar month, 2023–2026. Find your travel month, then look along the row for the greenest hour.
Best and worst months
December is the hardest month at SUN, with 78% of flights on time across 2023–2026; November is the best at 96%. Summer (June–August) runs 12 points worse than autumn: heavy schedules, peak loads and afternoon thunderstorms. Winter costs 13 points against autumn. Cancellations peak in December (2.5% of flights).
Airlines at SUN
United Airlines runs 44% of departures from SUN. Among airlines with at least 1,000 departures here, Delta Air Lines was the most reliable (92% on time) and United Airlines the least (77%), a 15-point difference. On a route where both fly, that difference is worth more than a small fare gap.
| Airline | Departures | On time | Left on time | Cancelled | Typical arrival |
|---|---|---|---|---|---|
| United Airlines | 1,415 | 77% | 81% | 0.4% | −11 min |
| Delta Air Lines | 1,131 | 92% | 93% | 0.8% | −16 min |
| Alaska Airlines | 474 | 78% | 78% | 2.3% | −8 min |
| American Airlines | 207 | 57% | 57% | 9.2% | +2 min |
Why flights are late at SUN
Airlines report a cause for every flight that arrives 15 or more minutes late. At SUN, 38% of delay minutes came from the airlines themselves: crew, maintenance, cleaning, fueling and baggage. Next is the air traffic system at 28%.
The average taxi from gate to takeoff is 19 minutes, about typical for a large U.S. airport.
Month by month
Over the latest 12 months 81% of SUN departures were on time, against 83% in the 12 months before, a decline of 1 points. The best recent month was November 2025 (96%); the worst, August 2026 (71%).
Worst cancellation days
The worst single day in the past year was Tuesday, Jan 20, 2026, when 27% of 11 scheduled departures were cancelled. Days like that are usually a major storm, a system outage or a holiday peak hitting bad weather. No average predicts them, so on a stormy forecast, check your airline's travel waivers.
| Date | Departures | Cancelled | On time |
|---|---|---|---|
| Jan 20, 2026 | 11 | 27% | 55% |
| Mar 13, 2026 | 14 | 21% | 57% |
| Feb 24, 2026 | 12 | 17% | 83% |
| Mar 11, 2026 | 13 | 15% | 69% |
| Jan 23, 2026 | 13 | 15% | 69% |
| Dec 24, 2025 | 15 | 13% | 60% |
| Dec 21, 2025 | 16 | 13% | 31% |
| Aug 11, 2026 | 10 | 10% | 70% |
| Dec 18, 2025 | 10 | 10% | 50% |
| Jul 28, 2026 | 10 | 10% | 70% |
Last flights of the day
The last flight of the day is a different bet. Across routes from SUN, each airline's final departure was cancelled 1.1% of the time, against 0.6% for its earlier flights (2.0× as often). Late in the day crews run short on duty hours, aircraft arrive late from elsewhere, and with no later flight to fold passengers into, cancelling is easier for the airline. 2.1% of last flights landed 3+ hours late. The riskiest last flight out was Alaska Airlines to Seattle (4.0% cancelled).
| Last flight to | Airline | Leaves | Cancelled | 3h+ late | On time |
|---|---|---|---|---|---|
| SEA Seattle | Alaska Airlines | 10:21 a.m. | 4.0% | 0.8% | 70% |
| DEN Denver | United Airlines | 2:38 p.m. | 0.4% | 3.7% | 77% |
| SLC Salt Lake City | Delta Air Lines | 3:15 p.m. | 0.8% | 1.4% | 92% |
Each airline's last scheduled departure of the day on a route, on days it flies the route at least twice; past 12 months. Riskiest first.
Tips for flying out of SUN
- Book the earliest departure you can live with. At SUN the 3 p.m. flights do best.
- Traveling in December? Leave extra slack for anything that can't move: cruises, weddings, the last connection of the day.
- Choosing between airlines? Delta Air Lines has the better record here.
- Need to arrive tonight? Don't book the last flight out of SUN; the one before it leaves you a backup.
- Delayed already? Most delays at SUN come from the airlines themselves. If your inbound plane is late, your flight will be too, whatever the board says.
Routes from SUN
Least reliable first. Routes with at least 365 flights a year.
| To | Flights | On time | Cancelled | Typical arrival |
|---|---|---|---|---|
| SEA Seattle | 468 | 79% | 1.9% | −8 min |
| DEN Denver | 630 | 84% | 0.2% | −15 min |
| SLC Salt Lake City | 1,078 | 93% | 0.7% | −16 min |
Flights into SUN
Arriving rather than leaving? These are the routes into Friedman Memorial, least reliable first. The weakest is from Denver (80% on time).
| From | Flights | On time | Cancelled |
|---|---|---|---|
| DEN Denver | 630 | 80% | 0.0% |
| SEA Seattle | 468 | 85% | 0.9% |
| SLC Salt Lake City | 1,078 | 92% | 0.7% |
Questions about SUN delays
What is the best time to fly out of SUN?
Flights scheduled at 3 p.m.: over the past year 92% of SUN departures at that hour arrived on time, against 77% at 2 p.m., the worst hour.
What month has the most flight delays at SUN?
December (78% on time). November is the best month (96%).
Which airline is most on time at SUN?
Delta Air Lines: 92% of its SUN departures arrived on time over the past year. United Airlines had the weakest record at 77%.
Why are flights delayed at SUN?
The biggest cause was the airlines themselves (38% of delay minutes): crew, maintenance, cleaning, fueling and baggage. Then the air traffic system (28%).
How often are flights cancelled at SUN?
1.4% of scheduled departures over the past 12 months, peaking in December at 2.5%.
Hours are scheduled local departure times. "On time" means arriving less than 15 minutes late at the destination; cancelled and diverted flights count as not on time. Method.