Route reliability record
BWI→GSP
Baltimore to Greer
- Flights
- 720
- Period
- September 2025 to August 2026
- Distance
- 426 mi
- Carriers
- 1
This route lands a B, 3 points better than the national rate of 77.3%. About one flight in five arrives 15 minutes late or worse, and those flights are late by about an hour on average. That rests on 720 BWI to GSP flights, with a median arrival 6 minutes early.
Best time to fly BWI to GSP: a 8am–11am departure, ideally on a Wednesday. Flights in that window arrived on time 93.3% of the time and Wednesday flights 86.5%, against 80.5% for the route overall.
The US average over the same twelve months is 77.3%, so there is little to separate this route from the country as a whole. The variation that matters here is internal: which carrier, and what time of day.
Key figures
On time
80.5%
Arrivals under 15 minutes late, of 707 completed flights
Avg delay
60 min
Across delayed arrivals only, not all flights
Cancelled
1.81%
National rate is 1.89%
Best carrier
Southwest
80.5% on time across 720 flights
These figures cover 720 flights between September 2025 and August 2026. The median arrival is 6 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.
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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 | 80.5% | 60 min | 1.81% | B |
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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 | 79.0% | 80.5% | 1.81% | 8am–11am, Wed | — |
| 2. DCA → GSPWashington to Greer | PSA Airlines | 59.6% | 63.0% | 5.39% | 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 23 points, against half a point between the best and worst carrier.
- 5am–8am—
- 8am–11am211 flights93.3%
- 11am–2pm142 flights83.8%
- 2pm–5pm17 flights—
- 5pm–8pm209 flights72.8%
- 8pm–5am141 flights70.1%
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 93.3% of the time, against 70.1% for the overnight window. That is 23 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 211 flights scheduled in it.
Explore
Filter BWI to GSP by airline, time, month and day
Pick a breakdown and a carrier. The dashed mark on each row is the same slice for every US flight.
On BWI to GSP, the best departure window is 8am–11am at 93.3% on time and the worst is 8pm–5am at 70.1%, a wide gap of 23.2 points. All US flights leaving 8am–11am ran 83.9%.
- 5–8am—
- 8–11am93.3%
- 11am–2pm83.8%
- 2–5pm—
- 5–8pm72.8%
- 8pm–5am70.1%
best all US flightsScale 60% to 100%. Cells under 30 flights show a dash.
Across the year
When delays peak on this route
This route's year swings by 26 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.
July is the worst month at 66.1% on time, 26 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 86.5% on time and Sunday the weakest at 74.7%, a spread of 12 points.
Delay causes
Why this route gets delayed
Late-arriving aircraft accounts for 43% of the 8,224 delay minutes carriers reported here, and the remaining four split what is left.
- 43%Late-arriving aircraft
- 37%Carrier
- 13%National Airspace System
- 6%Extreme weather
- 0%Security
43% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 8,224 reported delay minutes here, that single category outweighs weather by 7 to one. The split is drawn from 8,224 reported delay minutes.
The largest share of delay minutes, 37%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. It accounts for 3,029 of the 8,224 delay minutes reported here.
Cancellations sit at 1.81% against a national 1.89%, which is ordinary. Diversions add another 0.00%.
Connections and stage length
What a delay here actually costs
5.4% 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.
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 89.7% on time across 719 flights, 9 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 9 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 80.5% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 707 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 five arrives at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 19.5% of the 720 flights in this analysis, against 22.7% nationally. Delayed flights are late by about an hour on average.
How reliable is BWI to GSP compared with the rest of the country?
80.5% of flights arrive on time here against a national 77.3%, a difference of 3 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 93.3% on time. The 8pm–5am window is the weakest at 70.1%, 23 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 July delays on BWI to GSP?
July is the weakest month at 66.1% on time, compared with 91.7% in September. Across the year that is 26 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 route79.9%
- ATL to GSP, a related route83.7%
- BWI to MCO, a related route75.5%
- Southwest Airlines on-time record80.5%
- Why the first flight of the morning is statistically safest
- The best time of day to fly, according to 7.05 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, September 2025 to August 2026. Last updated ; recomputed monthly. How this data is collected.