Route reliability record
GSP→BWI
Greer to Baltimore
- Flights
- 719
- Period
- September 2025 to August 2026
- Distance
- 426 mi
- Carriers
- 1
This route earns an A. Close to nine flights in ten arrive inside the 15-minute window the DOT uses to define an on-time arrival, which puts it 12 points better than the national rate of 77.3%. When something does go wrong the average delay runs about an hour. That rests on 719 GSP to BWI flights, with a median arrival 9 minutes early.
Best time to fly GSP to BWI: a 5am–8am departure, ideally on a Tuesday. Flights in that window arrived on time 97.3% of the time and Tuesday flights 94.2%, against 89.7% for the route overall.
Set against the rest of the country, this route's record is 12 points better than the US average of 77.3%. That gap is worth roughly 124 fewer late arrivals for every thousand flights.
Key figures
On time
89.7%
Arrivals under 15 minutes late, of 706 completed flights
Avg delay
62 min
Across delayed arrivals only, not all flights
Cancelled
1.67%
National rate is 1.89%
Best carrier
Southwest
89.7% on time across 719 flights
These figures cover 719 flights between September 2025 and August 2026. The median arrival is 9 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 GSP to BWI
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 | 719 | 89.7% | 62 min | 1.67% | A |
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Best ways to make this trip
The most reliable ways to fly Greer to Baltimore
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. GSP → BWIGreer to Baltimore | Southwest Airlines | 88.2% | 89.7% | 1.67% | 5am–8am, Tue | — |
| 2. GSP → DCAGreer to Washington | PSA Airlines | 60.3% | 63.9% | 5.70% | 5am–8am, Sat (route) | OH 5031 07:38 |
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 29 points, against half a point between the best and worst carrier.
- 5am–8am76 flights97.3%
- 8am–11am289 flights94.7%
- 11am–2pm32 flights96.9%
- 2pm–5pm229 flights84.9%
- 5pm–8pm57 flights81.8%
- 8pm–5am36 flights68.6%
Scale runs 60% to 100%.
Book the early departure. Flights leaving between 5am–8am arrive on time 97.3% of the time, against 68.6% for the overnight window. That is 29 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 289 flights scheduled in it.
Explore
Filter GSP to BWI 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 GSP to BWI, the best departure window is 5am–8am at 97.3% on time and the worst is 8pm–5am at 68.6%, a wide gap of 28.7 points. All US flights leaving 5am–8am ran 89.3%.
- 5–8am97.3%
- 8–11am94.7%
- 11am–2pm96.9%
- 2–5pm84.9%
- 5–8pm81.8%
- 8pm–5am68.6%
best all US flightsScale 60% to 100%.
Across the year
When delays peak on this route
This route's year swings by 17 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 78.3% on time, 17 points below April, the best at 95.0%. 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, Tuesday is the strongest day at 94.2% on time and Monday the weakest at 82.7%, a spread of 12 points.
Delay causes
Why this route gets delayed
Late-arriving aircraft accounts for 55% of the 4,489 delay minutes carriers reported here, and the remaining four split what is left.
- 55%Late-arriving aircraft
- 28%Carrier
- 16%National Airspace System
- 1%Extreme weather
55% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 4,489 reported delay minutes here, that single category outweighs weather by 39 to one. The split is drawn from 4,489 reported delay minutes.
The practical consequence: the 5am–8am departure is the one that starts clean. Its aircraft has no earlier leg to be late from, which is exactly why that window shows 97.3% on time here.
Cancellations sit at 1.67% against a national 1.89%, which is ordinary. Diversions add another 0.14%.
Connections and stage length
What a delay here actually costs
Badly late arrivals are rare here: only 3.7% land an hour or more behind schedule, against 8.3% nationally. Connections built on this flight are about as safe as US domestic connections get, though a cancelled flight still ignores every layover you give it.
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 5am–8am window matters as much as it does.
The return leg is a different operation and performs like one: it runs 80.5% on time across 720 flights, 9 points below 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. 719 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 BWI after this flight
What to do with this
Booking this route
Put together: treat all of this as provisional. 719 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 89.7% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 706 completed flights over 12 months sit behind that.
Common questions
GSP to BWI questions
How often is GSP to BWI delayed?
About one flight in ten arrives at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 10.3% of the 719 flights in this analysis, against 22.7% nationally. Delayed flights are late by about an hour on average.
How reliable is GSP to BWI compared with the rest of the country?
89.7% of flights arrive on time here against a national 77.3%, a difference of 12 points in its favour. That is worth a A on this site's grading scale.
What time of day has the fewest delays on GSP to BWI?
The 5am–8am departure window is the strongest at 97.3% on time. The 8pm–5am window is the weakest at 68.6%, 29 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 GSP to BWI?
July is the weakest month at 78.3% on time, compared with 95.0% in April. Across the year that is 17 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
- BWI to GSP — the return legseparate record
- Baltimore/Washington International Thurgood Marshall (BWI) delay statistics
- GSP to ATL, a related route90.1%
- ATL to BWI, a related route75.2%
- GSP to ORD, a related route75.9%
- Southwest Airlines on-time record89.7%
- The most punctual routes in the US, and the least
- Why the first flight of the morning is statistically safest
Direction matters. GSP to BWI and BWI to GSP 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.