ON TIMEBOARD
Delta Air Lines / SDF → DTW

DL 3821 on time

Delta Air Lines 3821: Louisville to Detroit at 10:34 a.m.; Detroit to Louisville at 8:25 a.m. (past 12 months). Figures below the title are for SDF → DTW, its busiest leg

On time
86%
205 flights · likely 80–90%
Cancelled
1.5%
of scheduled flights
Typical arrival
−17 min
median vs schedule
When late
+77 min
average delay
Similar flights
84%
DL, same route & hour

About 1 in 7 DL 3821 flights from Louisville arrived 15+ minutes late, diverted or cancelled over the past year (14%); 1.5% were cancelled. The typical flight landed 17 minutes early.

DL 3821: SDF → DTW

Scheduled to leave Louisville at 10:34 a.m. local time, operated by SkyWest as OO 3821. Over the past year it arrived on time 86% of the time (205 flights), in line with other DL flights on the route at that hour (84%). Last seen in the data Aug 31, 2026.

Month by month

40%70%100%Aug 2024: 81% on time (31 flights)81AugSep 2024: too few flights (8 flights)SepMay 2025: 100% on time (20 flights)100MayJun 2025: too few flights (6 flights)JunJan 2026: 80% on time (25 flights)80JanFeb 2026: 78% on time (27 flights)78FebMar 2026: 81% on time (31 flights)81MarApr 2026: 93% on time (30 flights)93AprMay 2026: too few flights (6 flights)MayJun 2026: 88% on time (24 flights)88JunJul 2026: 90% on time (31 flights)90JulAug 2026: 90% on time (31 flights)90Aug

By day of week

DayFlightsOn time
Monday3184%
Tuesday3097%
Wednesday3087%
Thursday2979%
Friday2976%
Saturday2688%
Sunday3090%

Why it was late

Airline (crew, maintenance, ops) 73%Severe weather 21%Air traffic & airport (NAS) 6%

All flights SDF → DTW · Connecting off DL 3821? Check the risk

DL 3821: DTW → SDF

Scheduled to leave Detroit at 8:25 a.m. local time, operated by SkyWest as OO 3821. Over the past year it arrived on time 84% of the time (170 flights), in line with other DL flights on the route at that hour (82%). Last seen in the data Aug 31, 2026.

Month by month

40%70%100%Jul 2024: 83% on time (24 flights)83JulAug 2024: 81% on time (31 flights)81AugSep 2024: too few flights (8 flights)SepMay 2025: 90% on time (20 flights)90MayJun 2025: too few flights (6 flights)JunFeb 2026: 65% on time (17 flights)65FebMar 2026: 71% on time (31 flights)71MarApr 2026: 93% on time (30 flights)93AprMay 2026: too few flights (6 flights)MayJun 2026: 83% on time (24 flights)83JunJul 2026: 87% on time (31 flights)87JulAug 2026: 90% on time (31 flights)90Aug

By day of week

DayFlightsOn time
Monday2576%
Tuesday24100%
Wednesday2475%
Thursday2483%
Friday2475%
Saturday2483%
Sunday2592%

Why it was late

Airline (crew, maintenance, ops) 83%Air traffic & airport (NAS) 9%Severe weather 8%

All flights DTW → SDF · Connecting off DL 3821? Check the risk

Questions

How often is DL 3821 from SDF to DTW late?

Delta Air Lines 3821 from Louisville, KY to Detroit, MI arrived 15 or more minutes late, was diverted or was cancelled on 14% of 205 scheduled flights between September 2025 and August 2026. 1.5% were cancelled.

How often is DL 3821 from DTW to SDF late?

Delta Air Lines 3821 from Detroit, MI to Louisville, KY arrived 15 or more minutes late, was diverted or was cancelled on 16% of 170 scheduled flights between September 2025 and August 2026. 1.2% were cancelled.

Flight numbers change. Figures cover flights with this airline, number and route only. "Likely range" is the 95% interval for the true on-time rate given the number of flights. This is history, not live status: check Delta Air Lines for today's flight. Method.