Flight number record
F9 3599
Frontier Airlines · Atlanta to Denver
- Route
- ATL → DEN
- Departs
- 20:40
- Flights
- 259
- Period
- September 2025 to August 2026
Historical statistics for September 2025 to August 2026, not live status. For today’s F9 3599, check with Frontier Airlines.
F9 3599 draws a D. Roughly one flight in three arrives at least 15 minutes late, and the typical late arrival is an hour and a half behind schedule. Build slack into anything you connect to. That rests on 259 flights, with a median arrival 4 minutes late.
The national on-time rate over the same period is 77.3%, so F9 3599 runs 17 points behind the country as a whole. Across a thousand flights that is about 166 extra late arrivals.
Key figures
On time
60.7%
Arrivals under 15 minutes late, of 252 completed flights
Avg delay
84 min
Across delayed arrivals only, not all flights
Cancelled
2.70%
National rate is 1.89%
1 hour+ late
15.5%
National rate is 8.3%
These figures cover 259 flights between September 2025 and August 2026. Beyond the headline rate, 15.5% of arrivals land a full hour or more behind schedule, against 8.3% nationally.
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Schedule
When F9 3599 flies
F9 3599 flies ATL to DEN without a single fixed slot. Its most common scheduled departure was 20:40, used on 60 of 259 flights, with 20:30 (47 flights) and 20:00 (27 flights) next.
- Departs 20:4060 flights23.2%
- Departs 20:3047 flights18.1%
- Departs 20:0027 flights10.4%
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 20:40 departure sits in the 8pm–5am window. Across every US flight scheduled in that window the on-time rate is 70.1%, and F9 3599 runs 9 points worse at 60.7%. 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
F9 3599 next to ATL to DEN
Every carrier on ATL to DEN combined arrived on time 78.0% of the time across 5,594 flights, so F9 3599 is 17 points behind it. Frontier flew 793 flights on the same city pair under all its flight numbers, including this one, and those ran 71.2% on time. Across its whole network Frontier Airlines managed 72.7%, which this flight trails by 12 points.
| Compared with | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| F9 3599thin sample | 259 | 60.7% | 84 min | 2.70% | D |
| All Frontier Airlines on ATL–DEN | 793 | 71.2% | 79 min | 1.39% | C |
| All carriers on ATL–DEN | 5,594 | 78.0% | 61 min | 1.11% | B |
| Frontier Airlines, whole network | 213,022 | 72.7% | 84 min | 2.05% | C |
Across the year
F9 3599 quarter by quarter
F9 3599 did not run the same all year. Its best quarter was Oct–Dec 2025 at 70.3% on time and its weakest Jul–Sep 2026 at 43.9%, a swing of 26 points on roughly 65 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 202538 flights70.3%
- Jan–Mar 202671 flights65.2%
- Apr–Jun 202690 flights64.0%
- Jul–Sep 202660 flights43.9%
Scale runs 35% to 75%.
By weekday, F9 3599 did best on Thursday at 80.0% on time and worst on Saturday at 38.2%. Each day rests on about 37 flights, so a gap of 42 points is worth noticing but could still narrow in another year.
Arrival by arrival
How late F9 3599 runs when it is late
F9 3599 often beats the schedule: 65 of 252 completed flights, 26%, arrived 15 minutes or more early. The 99 late arrivals split 26 under half an hour, 34 between 30 and 60 minutes, and 39 an hour or more.
- 15+ min early65 flights25.8%
- Within 15 min88 flights34.9%
- 15–29 min late26 flights10.3%
- 30–59 min late34 flights13.5%
- 1–2 hours late24 flights9.5%
- 2+ hours late15 flights6.0%
Scale runs 0% to 100%.
Share of 252 completed flights by arrival against schedule.
33 of 119 late departures made up the time and arrived on time, 28% of them. In the other direction, 13 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 DEN.
The worst days
Worst days for F9 3599
The latest arrival of the period was on 31 December 2025, 15 hours 27 minutes behind schedule; most of its delay minutes were filed as carrier-caused (crew, maintenance, fuelling, baggage). On three of the five worst days the largest share was filed as a late-arriving aircraft.
| Date | Arrived late by | Largest filed cause |
|---|---|---|
| 31 December 2025 | 15 hours 27 minutes | Carrier |
| 9 March 2026 | 15 hours | Extreme weather |
| 1 December 2025 | 3 hours 51 minutes | Late-arriving aircraft |
| 4 August 2026 | 3 hours 46 minutes | Late-arriving aircraft |
| 24 February 2026 | 3 hours 10 minutes | Late-arriving aircraft |
Delay causes
Why F9 3599 runs late
Late-arriving aircraft accounts for 48% of the 8,281 delay minutes carriers reported here, and the remaining four split what is left.
- 48%Late-arriving aircraft
- 29%Carrier
- 12%National Airspace System
- 11%Extreme weather
Extreme weather accounts for 11% 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 1.8 times the usual weather exposure. The split is drawn from 8,281 delay minutes reported on F9 3599.
Cancellations run at 2.70%, 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
15.5% 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 1,199 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.
Every one of the 259 flights under F9 3599 in the data flew ATL to DEN. The number was not reused on any other city pair, which makes this a clean record of one route.
One caution: this is a thin sample. 259 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 F9 3599
For a booking, the cancellation rate is the figure to plan around on F9 3599: 2.70% of its 259 scheduled flights did not operate. A late arrival costs an hour and a half, but a cancellation costs the day, so leave a later option open.
Related
Where to go next
- ATL to DEN, every carrier and departure
- DEN to ATL, the return direction
- Delta Air Lines 519 on the same route66.7%
- United Airlines 235 on the same route78.5%
- Delta Air Lines 746 on the same route67.8%
- Delta Air Lines 706 on the same route84.7%
- Frontier Airlines 3293 on the same route81.2%
- Delta Air Lines 530 on the same route80.5%
- Hartsfield-Jackson Atlanta International (ATL) delay statistics
- Denver International (DEN) delay statistics
- Frontier Airlines on-time record
- Every Frontier Airlines 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 Frontier 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.