Flight Reliability
DL 638 · Delta Air Lines
Boston → Atlanta (BOS–ATL)87% of its flights flew this route. The rest (BUF–DTW, EWR–SLC) are included in these numbers.
- 77%
- Arrive within 15 minutes
- 8 min
- Average arrival delay
- 1.5%
- Cancelled
- 4 min early
- Median arrival delay
Based on 327 historical flights. Data through May 2026.
What the data says
The 3–6 PM departure wins.
DL 638 departing between 3–6 PM arrived on time 78% of the time, versus 70% between 6–9 AM.
Thursdays have been rough.
DL 638 arrived on time 90% of the time on Wednesdays and just 64% on Thursdays. That gap is worth planning around.
A bit behind the Delta Air Lines network.
DL 638 arrived on time 77% of the time, versus 81% across the Delta Air Lines network.
Trending in the right direction.
DL 638 arrived on time 95% of the time over the last three months in the data, compared with 67% in the three months before that.
The breakdown
- Mon71%(45 flights)
- Tue77%(48 flights)
- Wed90%(48 flights)
- Thu64%(45 flights)
- Fri78%(45 flights)
- Sat71%(42 flights)
- Sun85%(47 flights)
- 6–9 AM70%(37 flights)
- 3–6 PM78%(283 flights)
Jun 67% → May 100% on time
| Month | On-time percentage | Flights |
|---|---|---|
| June 2025 | 67% | 30 |
| July 2025 | 66% | 29 |
| August 2025 | 86% | 29 |
| September 2025 | 70% | 30 |
| October 2025 | 71% | 31 |
| November 2025 | 80% | 30 |
| December 2025 | 60% | 30 |
| January 2026 | 77% | 30 |
| February 2026 | 64% | 11 |
| March 2026 | 91% | 21 |
| April 2026 | 95% | 21 |
| May 2026 | 100% | 28 |
- Departures on time
- 74%
- Diverted
- 0.6%
- Flights flown
- 320
- Months covered
- 12
Same route, other flights
Keep nerding
Based on 327 historical flights, because apparently we checked. Historical flight data: U.S. Bureau of Transportation Statistics, June 2025 – May 2026. Data through May 2026. How we calculate this.