Route reliability record
BWI→GSP
Baltimore to Greer
- Flights
- 720
- Period
- July 2025 to June 2026
- Distance
- 426 mi
- Carriers
- 1
This route lands a B, 5 points better than the national rate of 77.6%. About one flight in six arrives 15 minutes late or worse, and those flights are late by a little over an hour on average. That is a workable record, not a spotless one. That rests on 720 BWI to GSP flights, with a median arrival 7 minutes early.
Best time to fly BWI to GSP: a 8am–11am departure, ideally on a Wednesday. Flights in that window arrived on time 92.9% of the time and Wednesday flights 85.6%, against 82.1% for the route overall.
Set against the rest of the country, this route's record is 5 points better than the US average of 77.6%. That gap is worth roughly 45 fewer late arrivals for every thousand flights.
Key figures
On time
82.1%
Arrivals under 15 minutes late, of 711 completed flights
Avg delay
73 min
Across delayed arrivals only, not all flights
Cancelled
1.25%
National rate is 1.81%
Best carrier
Southwest
82.1% on time across 720 flights
These figures cover 720 flights between July 2025 and June 2026. The median arrival is 7 minutes early, which is the part an average hides: most flights here are fine, and the on-time rate is decided by a tail of badly late ones. On-time means under 15 minutes late, the DOT's own threshold.
Carrier by carrier
Which airline is most reliable on BWI to GSP
Only one carrier clears this site's 365-flight floor here, so there is no comparison to draw. The table below is the full picture.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| Southwest Airlines | 720 | 82.1% | 73 min | 1.25% | B |
Best ways to make this trip
The most reliable ways to fly Baltimore to Greer
Every airline on this route and on the routes between nearby airports, ranked by how often a scheduled flight actually operated and arrived on time. 1 of the top 2 use a different airport at one end.
| Option | Airline | Success | On time | Cancelled | Best departure | Most punctual flight |
|---|---|---|---|---|---|---|
| 1. BWI → GSPBaltimore to Greer | Southwest Airlines | 81.1% | 82.1% | 1.25% | 8am–11am, Wed | — |
| 2. DCA → GSPWashington to Greer | PSA Airlines | 61.7% | 65.2% | 5.31% | 8am–11am, Tue (route) | — |
Success is the share of scheduled flights that operated and arrived less than 15 minutes late, so a cancelled flight counts against it. “(route)” means the best time comes from every carrier on the route rather than this airline alone.
Departure window
The best time of day to leave
Departure time matters more here than the choice of carrier. The gap between the best and worst window is 27 points, against half a point between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am—
- 8am–11am256 flights92.9%
- 11am–2pm109 flights89.0%
- 2pm–5pm8 flights—
- 5pm–8pm204 flights76.0%
- 8pm–5am143 flights66.4%
Scale runs 60% to 100%. Rows with fewer than 30 flights show a dash.
Book the morning departure. Flights leaving between 8am–11am arrive on time 92.9% of the time, against 66.4% for the overnight window. That is 27 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 8am–11am window is the busiest, with 256 flights scheduled in it.
Across the year
When delays peak on this route
This route's year swings by 24 points from best month to worst, which is wide. An annual average tells you very little about the week you are actually flying, so read the strip rather than the headline if your dates are fixed.
June is the worst month at 67.8% on time, 24 points below September, the best at 91.7%. Summer afternoon convection and peak-season schedules land on the same weeks every year, so this is a pattern you can book around rather than a run of bad luck. January was the busiest month here, with 62 flights.
Across the week, Wednesday is the strongest day at 85.6% on time and Monday the weakest at 76.0%. 10 points is a smaller lever than departure hour, but it is free.
Delay causes
Why this route gets delayed
One category carries most of the weight here. Late-arriving aircraft accounts for 53% of the 9,223 delay minutes carriers reported, and the remaining four split what is left. The split is by minutes rather than by flights, so a few very long delays count for as much as many short ones.
- 53%Late-arriving aircraft
- 32%Carrier
- 8%National Airspace System
- 7%Extreme weather
53% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. That is a cascade, and cascades start small and grow through the day. Across 9,223 reported delay minutes here, that single category outweighs weather by 8 to one. It is the strongest argument for booking the first departure of the morning, when the aircraft has been sitting at the gate overnight with nothing to inherit. The split is drawn from 9,223 reported delay minutes.
The practical consequence: the 8am–11am departure is the one that starts clean. Its aircraft has no earlier leg to be late from, which is exactly why that window shows 92.9% on time here.
Cancellations sit at 1.25% against a national 1.81%, which is ordinary. Diversions add another 0.00%.
Connections and stage length
What a delay here actually costs
6.8% of arrivals land an hour or more late, close to the national 8.1%. That is the figure that decides a connection, and it says a 60 to 75 minute layover is reasonable here while anything under 45 minutes is a bet. Most delays on this route last a little over an hour, which a normal layover absorbs.
At 426 miles this is a short hop, and stage length matters more than it looks. A flight this short spends under two hours in the air, which leaves almost nothing to claw back a late pushback with. Delay here is decided on the ground, in the turn, which is why the 8am–11am window matters as much as it does.
The return leg is a different operation and performs like one: it runs 89.5% on time across 719 flights, 7 points above this direction. Departure banks, aircraft rotations and the congestion at each end all differ, so scoring the two directions together would average away a real 7 points of difference.
One caution: this is a thin sample. 720 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.
Work out the risk of missing a connection in GSP after this flight
What to do with this
Booking this route
Put together: treat all of this as provisional. 720 flights over twelve months is enough to clear this site's floor and not enough to be confident to better than a couple of points. The 82.1% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 711 completed flights over 12 months sit behind that.
Common questions
BWI to GSP questions
How often is BWI to GSP delayed?
About one flight in six arrives at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 17.9% of the 720 flights in this analysis, against 22.4% nationally. Delayed flights are late by a little over an hour on average.
How reliable is BWI to GSP compared with the rest of the country?
82.1% of flights arrive on time here against a national 77.6%, a difference of 5 points in its favour. That is worth a B on this site's grading scale.
What time of day has the fewest delays on BWI to GSP?
The 8am–11am departure window is the strongest at 92.9% on time. The 8pm–5am window is the weakest at 66.4%, 27 points behind. Later departures inherit delays from earlier flights the same aircraft has already flown, which is why the curve slopes the way it does.
How bad are June delays on BWI to GSP?
June is the weakest month at 67.8% on time, compared with 91.7% in September. Across the year that is 24 points between the best and worst months. Moving flexible dates out of that month is one of the few things that reliably helps.
Related
Where to go next
- GSP to BWI — the return legseparate record
- Baltimore/Washington International Thurgood Marshall (BWI) delay statistics
- BWI to ATL, a related route80.6%
- ATL to GSP, a related route83.9%
- BWI to MCO, a related route75.6%
- Southwest Airlines on-time record82.1%
- Why the first flight of the morning is statistically safest
- The best time of day to fly, according to 7.04 million flight records
Direction matters. BWI to GSP and GSP to BWI are scored separately because they are separate operations, with different departure banks and different aircraft. Compare the return leg.
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Source: US DOT Bureau of Transportation Statistics, on-time performance data, July 2025 to June 2026. Last updated 15 September 2026; recomputed monthly. How this data is collected.