Flight number record
DL 1633
Delta Air Lines · Detroit to Houston
- Route
- DTW → IAH
- Departs
- 20:15
- Flights
- 364
- Period
- September 2025 to August 2026
Historical statistics for September 2025 to August 2026, not live status. For today’s DL 1633, check with Delta Air Lines.
DL 1633 lands a B+, level with the national rate of 77.3%. Roughly one flight in four arrives 15 minutes late or worse, and those flights are late by about an hour on average. That rests on 364 flights, with a median arrival 6 minutes early.
Key figures
On time
77.5%
Arrivals under 15 minutes late, of 360 completed flights
Avg delay
67 min
Across delayed arrivals only, not all flights
Cancelled
0.82%
National rate is 1.89%
1 hour+ late
8.9%
National rate is 8.3%
These figures cover 364 flights between September 2025 and August 2026. Beyond the headline rate, 8.9% of arrivals land a full hour or more behind schedule, against 8.3% nationally.
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Schedule
When DL 1633 flies
DL 1633 flies DTW to IAH without a single fixed slot. Its most common scheduled departure was 20:15, used on 95 of 364 flights, with 20:48 (60 flights) and 20:25 (57 flights) next.
- Departs 20:1595 flights26.1%
- Departs 20:4860 flights16.5%
- Departs 20:2557 flights15.7%
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 20:15 departure sits in the 8pm–5am window. Across every US flight scheduled in that window the on-time rate is 70.1%, and DL 1633 runs 7 points better at 77.5%. 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
DL 1633 next to DTW to IAH
Every carrier on DTW to IAH combined arrived on time 78.5% of the time across 2,083 flights, so DL 1633 is about level with it. Delta flew 1,327 flights on the same city pair under all its flight numbers, including this one, and those ran 78.6% on time. Across its whole network Delta Air Lines managed 81.1%, which this flight trails by 4 points.
| Compared with | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| DL 1633thin sample | 364 | 77.5% | 67 min | 0.82% | B+ |
| All Delta Air Lines on DTW–IAH | 1,327 | 78.6% | 56 min | 0.75% | B+ |
| All carriers on DTW–IAH | 2,083 | 78.5% | 62 min | 0.96% | B+ |
| Delta Air Lines, whole network | 1,039,517 | 81.1% | 71 min | 1.74% | B |
Across the year
DL 1633 quarter by quarter
DL 1633 did not run the same all year. Its best quarter was Jul–Sep 2025 at 90.0% on time and its weakest Jul–Sep 2026 at 62.9%, a swing of 27 points on roughly 73 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.
- Jul–Sep 202530 flights90.0%
- Oct–Dec 202591 flights77.8%
- Jan–Mar 202690 flights82.8%
- Apr–Jun 202691 flights78.0%
- Jul–Sep 202662 flights62.9%
Scale runs 55% to 95%.
By weekday, DL 1633 ranged from 74.5% on Thursday to 80.8% on Wednesday. With about 52 flights behind each day, a spread of 6 points is inside normal variation, so the day you fly is not worth changing for this flight.
Arrival by arrival
How late DL 1633 runs when it is late
DL 1633 often beats the schedule: 121 of 360 completed flights, 34%, arrived 15 minutes or more early. The 81 late arrivals split 26 under half an hour, 23 between 30 and 60 minutes, and 32 an hour or more.
- 15+ min early121 flights33.6%
- Within 15 min158 flights43.9%
- 15–29 min late26 flights7.2%
- 30–59 min late23 flights6.4%
- 1–2 hours late18 flights5.0%
- 2+ hours late14 flights3.9%
Scale runs 0% to 100%.
Share of 360 completed flights by arrival against schedule.
30 of 102 late departures made up the time and arrived on time, 29% of them. 9 flights left on time and still arrived late.
The worst days
Worst days for DL 1633
The latest arrival of the period was on 25 January 2026, 4 hours 28 minutes behind schedule; most of its delay minutes were filed as carrier-caused (crew, maintenance, fuelling, baggage). The same cause led on five of the five worst days.
| Date | Arrived late by | Largest filed cause |
|---|---|---|
| 25 January 2026 | 4 hours 28 minutes | Carrier |
| 14 June 2026 | 3 hours 52 minutes | Carrier |
| 19 May 2026 | 3 hours 35 minutes | Carrier |
| 24 April 2026 | 3 hours 17 minutes | Carrier |
| 30 November 2025 | 3 hours 5 minutes | Carrier |
Delay causes
Why DL 1633 runs late
Carrier accounts for 60% of the 5,415 delay minutes carriers reported here, and the remaining four split what is left.
- 60%Carrier
- 26%Late-arriving aircraft
- 14%National Airspace System
- 0%Extreme weather
The largest share of delay minutes, 60%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. It accounts for 3,227 of the 5,415 delay minutes reported here. The split is drawn from 5,415 delay minutes reported on DL 1633.
Cancellations are rare at 0.82%, below the national 1.89% and low enough to earn the plus on the grade. Roughly one flight in 100 is called off; the risk here is arriving late, not not arriving.
Connections and routes
What a delay on this flight costs
8.9% of arrivals land an hour or more late, close to the national 8.3%, so a 60 to 75 minute layover is reasonable here while anything under 45 minutes is a bet. Most delays on this route last about an hour, which a normal layover absorbs.
The 1,075 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 364 flights under DL 1633 in the data flew DTW to IAH. 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. 364 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 DL 1633
For a booking, read DL 1633 as 77.5% on time with 0.82% cancelled over 364 flights. Those are rates from the past twelve months, not a forecast for any particular day.
Related
Where to go next
- DTW to IAH, every carrier and departure
- IAH to DTW, the return direction
- Detroit Metropolitan Wayne County (DTW) delay statistics
- George Bush Intercontinental (IAH) delay statistics
- Delta Air Lines on-time record
- Every Delta Air Lines flight number with a record
- The most and least reliable flight numbers in the US
- The best time of day to fly, according to 7.05 million flight records
A flight number here means Delta Air Lines’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.