Flight Reliability
DL 859 · Delta Air Lines
Boston → Salt Lake City (BOS–SLC)
90
Nerd Approved
WanderNerd Reliability Score
- 90%
- Arrive within 15 minutes
- 6 min early
- Average arrival delay
- 1.6%
- Cancelled
- 9 min early
- Median arrival delay
Based on 365 historical flights. Data through May 2026.
What the data says
Skip Saturday if you can.
DL 859 arrived on time 94% of the time on Fridays. On Saturdays: 81%.
Better than the BOS–SLC route average.
DL 859 arrived on time 90% of the time, versus 77% across the BOS–SLC route.
Better than the Delta Air Lines network average.
DL 859 arrived on time 90% of the time, versus 81% across the Delta Air Lines network.
Trending in the right direction.
DL 859 arrived on time 91% of the time over the last three months in the data, compared with 76% in the three months before that.
The breakdown
- Mon92%(50 flights)
- Tue94%(49 flights)
- Wed92%(50 flights)
- Thu90%(52 flights)
- Fri94%(52 flights)
- Sat81%(52 flights)
- Sun87%(53 flights)
90%
May
Jun 97% → May 90% on time
| Month | On-time percentage | Flights |
|---|---|---|
| June 2025 | 97% | 30 |
| July 2025 | 97% | 31 |
| August 2025 | 97% | 30 |
| September 2025 | 100% | 30 |
| October 2025 | 94% | 31 |
| November 2025 | 90% | 30 |
| December 2025 | 81% | 31 |
| January 2026 | 68% | 28 |
| February 2026 | 81% | 26 |
| March 2026 | 94% | 31 |
| April 2026 | 90% | 30 |
| May 2026 | 90% | 30 |
- Departures on time
- 96%
- Diverted
- 0.3%
- Flights flown
- 358
- Months covered
- 12
Same route, other flights
Keep nerding
Based on 365 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.