FlyerIntel

FlyerIntel Research

Routes That Lose the Most On-Time in Summer

CLT → JAX falls 19.3 points between the rest of the year and June to August.

Published October 18, 2026 · Source period July 2023 – July 2026

Summary

59.6% of completed flights on CLT → JAX arrived on time in summer, against 78.9% in the other months, the largest drop of 1,630 routes. Across all of them the gap was 7.5 points.

Key findings

  • CLT → JAX lost 19.3 points of on-time arrival in June to August, from 78.9% to 59.6%.
  • 72.5% of completed flights on the listed routes arrived on time in summer, 80.0% in the other months.
  • 1,603 of 1,630 routes were worse in summer than in the rest of the year.
  • The median route moved +7.4 points from the other months to summer, counted as other months less summer.
  • SBA → SFO changed least, -0.1 points.

Summer against the rest of the year

Across the 1,630 routes listed, 72.5% of completed flights arrived on time in June, July and August, against 80.0% in the other nine months, a gap of 7.5 points. 1,603 of the 1,630 routes was worse in summer. CLT → JAX lost the most: 78.9% on time outside summer, 59.6% in summer, 19.3 points. SBA → SFO changed least, -0.1 points.

The 25 routes that lose the most on-time performance in summer, points

CLT → JAX · 78.9% outside summer, 59.6% in summer19.3 points
LAS → MCO · 78.9% outside summer, 60.1% in summer18.8 points
CLT → MCO · 76.0% outside summer, 57.3% in summer18.7 points
SEA → MDW · 87.4% outside summer, 69.1% in summer18.3 points
DFW → SMF · 72.3% outside summer, 54.3% in summer17.9 points
CLT → SEA · 75.1% outside summer, 57.5% in summer17.6 points
DFW → SJU · 74.7% outside summer, 57.2% in summer17.5 points
LAS → PHL · 85.6% outside summer, 68.3% in summer17.3 points
PHL → PIT · 82.5% outside summer, 65.3% in summer17.2 points
DFW → MCI · 74.5% outside summer, 57.5% in summer17.0 points
CLT → DEN · 78.0% outside summer, 61.3% in summer16.7 points
IAH → MCO · 81.9% outside summer, 65.3% in summer16.5 points
IAH → PHL · 84.3% outside summer, 68.1% in summer16.2 points
PHL → LAS · 79.1% outside summer, 63.1% in summer16.0 points
IAH → BWI · 81.7% outside summer, 65.7% in summer15.9 points
JFK → DTW · 81.0% outside summer, 65.1% in summer15.9 points
DEN → MIA · 75.7% outside summer, 59.8% in summer15.9 points
CLT → TPA · 77.1% outside summer, 61.3% in summer15.8 points
BWI → PIT · 79.2% outside summer, 63.4% in summer15.8 points
MDW → SEA · 72.3% outside summer, 56.5% in summer15.8 points
CLT → MCI · 79.0% outside summer, 63.2% in summer15.7 points
CLT → IND · 77.4% outside summer, 61.7% in summer15.7 points
DEN → MEM · 78.8% outside summer, 63.2% in summer15.6 points
CLT → BWI · 77.9% outside summer, 62.3% in summer15.6 points
BWI → MCI · 78.2% outside summer, 62.7% in summer15.5 points

Routes with the largest summer drop

Routes with the largest summer drop
#RouteFromToOn time, other monthsOn time, summerDrop, pointsCompleted flights in summer
1CLT → JAXCharlotteJacksonville78.9%59.6%19.31,706
2LAS → MCOLas VegasOrlando78.9%60.1%18.81,268
3CLT → MCOCharlotteOrlando76.0%57.3%18.74,058
4SEA → MDWSeattleChicago87.4%69.1%18.3792
5DFW → SMFDallas–Fort WorthSacramento72.3%54.3%17.91,535
6CLT → SEACharlotteSeattle75.1%57.5%17.61,393
7DFW → SJUDallas–Fort WorthSan Juan74.7%57.2%17.5890
8LAS → PHLLas VegasPhiladelphia85.6%68.3%17.31,447
9PHL → PITPhiladelphiaPittsburgh82.5%65.3%17.21,454
10DFW → MCIDallas–Fort WorthKansas City74.5%57.5%17.02,179
11CLT → DENCharlotteDenver78.0%61.3%16.72,438
12IAH → MCOHoustonOrlando81.9%65.3%16.52,874
13IAH → PHLHoustonPhiladelphia84.3%68.1%16.21,751
14PHL → LASPhiladelphiaLas Vegas79.1%63.1%16.01,468
15IAH → BWIHoustonBaltimore81.7%65.7%15.9975
16JFK → DTWNew YorkDetroit81.0%65.1%15.91,338
17DEN → MIADenverMiami75.7%59.8%15.91,915
18CLT → TPACharlotteTampa77.1%61.3%15.82,692
19BWI → PITBaltimorePittsburgh79.2%63.4%15.8883
20MDW → SEAChicagoSeattle72.3%56.5%15.8787
21CLT → MCICharlotteKansas City79.0%63.2%15.71,099
22CLT → INDCharlotteIndianapolis77.4%61.7%15.71,602
23DEN → MEMDenverMemphis78.8%63.2%15.61,103
24CLT → BWICharlotteBaltimore77.9%62.3%15.62,775
25BWI → MCIBaltimoreKansas City78.2%62.7%15.5895

On-time arrival is arrivals within 15 minutes over completed flights, the same months in numerator and denominator. Summer is June, July and August of every year in the data; the other months are the remaining nine. A route needs 750 completed flights in each group, 4 summer months and 8 other months of data; 1,140 routes are left out. 1,513 of the 1,603 routes with a drop have a gap more than 2 standard errors wide, a guard against naming a tie, not an interval.

Routes that were better in summer

Routes that were better in summer
RouteOn time, other monthsOn time, summerChange, pointsCompleted flights in summer
FLL → AUS63.4%70.6%+7.3797
HNL → OAK84.0%90.3%+6.3764
SJU → DFW73.2%78.6%+5.4878
FLL → SFO75.2%79.2%+4.0926
HNL → SAN80.4%83.5%+3.11,408

The routes where the summer rate was highest above the rate in the other months, in the same listing.

What this does not show

The data does not start in January and does not end in December, so some calendar months occur in more years than others and the other nine months are not balanced. A route that runs only in summer is left out by the month requirement. Summer here is a calendar window, not a weather finding: the monthly aggregates carry no cause for a delay beyond the DOT’s cause totals, which are not used. A route can lose on-time performance in summer because of its origin, its destination or the airspace between them, and this report does not separate them. Cancelled flights are not in the on-time rate, so a route that cancelled more in summer can look better here than it was.

Pages for what this report covers

Airports: Charlotte (CLT) · Jacksonville (JAX) · Santa Barbara (SBA) · San Francisco (SFO) · Las Vegas (LAS) · Orlando (MCO) · Seattle (SEA) · Chicago (MDW) · Dallas–Fort Worth (DFW) · Sacramento (SMF)

Routes: CLT → MCO

Methodology

Calculated by FlyerIntel from 21,708,321 individual flight records in the US Department of Transportation Bureau of Transportation Statistics Reporting Carrier On-Time Performance dataset, covering July 2023 through July 2026. Following BTS methodology, a flight counts as delayed when it arrives 15 or more minutes after its scheduled arrival time. Cancelled and diverted flights have no arrival time and are excluded from on-time rates rather than counted as late; cancellation rates are reported separately. Full definitions are published at /methodology/. On-time rates are counted from the monthly rows of each route between covered airports: arrivals within 15 minutes over completed flights, with June, July and August pooled and the other nine months pooled across every year in the data. The drop is the rate outside summer less the rate in summer, in points.

Limitations

The source dataset covers scheduled domestic flights operated by carriers above the DOT reporting threshold; smaller carriers and international flights are not included. Flights sold under a mainline brand but flown by a regional carrier are attributed to the operating carrier, which is how the DOT records them. Past performance describes what has happened and is not a prediction about any individual flight.

Sources

  • FlyerIntel analysis — FlyerIntel · source
  • Reporting Carrier On-Time Performance — US Department of Transportation, Bureau of Transportation Statistics · source

Full FlyerIntel methodology · Report a problem with this analysis