Route reliability record
GSP→BWI
Greer to Baltimore
- Flights
- 719
- Period
- July 2025 to June 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 77.6%. When something does go wrong the average delay runs about an hour. That rests on 719 GSP to BWI flights, with a median arrival 10 minutes early.
Best time to fly GSP to BWI: a 5am–8am departure, ideally on a Saturday. Flights in that window arrived on time 95.1% of the time and Saturday flights 93.5%, against 89.5% for the route overall.
Set against the rest of the country, this route's record is 12 points better than the US average of 77.6%. That gap is worth roughly 119 fewer late arrivals for every thousand flights.
Key figures
On time
89.5%
Arrivals under 15 minutes late, of 708 completed flights
Avg delay
65 min
Across delayed arrivals only, not all flights
Cancelled
1.53%
National rate is 1.81%
Best carrier
Southwest
89.5% on time across 719 flights
These figures cover 719 flights between July 2025 and June 2026. The median arrival is 10 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 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 | 89.5% | 65 min | 1.53% | A |
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 | 88.1% | 89.5% | 1.53% | 5am–8am, Sat | — |
| 2. GSP → DCAGreer to Washington | PSA Airlines | 63.1% | 66.6% | 5.21% | 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 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–8am124 flights95.1%
- 8am–11am241 flights94.9%
- 11am–2pm19 flights—
- 2pm–5pm227 flights87.9%
- 5pm–8pm72 flights74.3%
- 8pm–5am36 flights68.6%
Scale runs 60% to 100%. Rows with fewer than 30 flights show a dash.
Book the early departure. Flights leaving between 5am–8am arrive on time 95.1% of the time, against 68.6% 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 241 flights scheduled in it.
Across the year
When delays peak on this route
This route's year swings by 23 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 72.1% on time, 23 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, Saturday is the strongest day at 93.5% on time and Monday the weakest at 81.4%. 12 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 4,813 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
- 26%Carrier
- 18%National Airspace System
- 3%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 4,813 reported delay minutes here, that single category outweighs weather by 18 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 4,813 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 95.1% on time here.
Cancellations sit at 1.53% against a national 1.81%, which is ordinary. Diversions add another 0.00%.
Connections and stage length
What a delay here actually costs
Badly late arrivals are rare here: only 4.4% land an hour or more behind schedule, against 8.1% 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 82.1% on time across 720 flights, 7 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 7 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 89.5% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 708 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 10.5% of the 719 flights in this analysis, against 22.4% nationally. Delayed flights are late by about an hour on average.
How reliable is GSP to BWI compared with the rest of the country?
89.5% of flights arrive on time here against a national 77.6%, 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 95.1% on time. The 8pm–5am window is the weakest at 68.6%, 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 July delays on GSP to BWI?
July is the weakest month at 72.1% on time, compared with 95.0% in April. Across the year that is 23 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 route90.4%
- ATL to BWI, a related route75.6%
- GSP to ORD, a related route74.9%
- Southwest Airlines on-time record89.5%
- 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. 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, July 2025 to June 2026. Last updated 15 September 2026; recomputed monthly. How this data is collected.