Route reliability record

PHL→BOS

Philadelphia to Boston

Flights: 4,956
Period: July 2025 to June 2026
Distance: 280 mi
Carriers: 4

This route sits in the middle of the pack with a B. Close to three flights in four arrive on time by the DOT's definition, 2 points worse than the national rate of 77.6%. The late ones land a little over an hour behind schedule. That rests on 4,956 flights, of which Republic Airways flew 1,761 at 80.9% on time.

Republic Airways is the most reliable of the three carriers covered here at 80.9% on time across 1,761 flights.

On time

75.2%

Arrivals under 15 minutes late, of 4,811 completed flights

Avg delay

79 min

Across delayed arrivals only, not all flights

Cancelled

2.93%

National rate is 1.81%

Best carrier

Republic

80.9% on time across 1,761 flights

These figures cover 4,956 flights between July 2025 and June 2026. Beyond the headline rate, 12.0% of arrivals land a full hour or more behind schedule. That is the number that wrecks a connection, and it is not visible in an on-time percentage alone.

Carrier by carrier

Which airline is most reliable on PHL to BOS

The choice of carrier is not cosmetic here. Republic Airways arrives on time 80.9% of the time; American Airlines manages 71.4%. Sample sizes sit next to every figure, because a two-point gap across 2,246 flights means less than a ten-point one.

On-time performance by carrier on PHL to BOS
Airline	Flights	On time	Avg delay	Cancelled	Grade
Frontier Airlinesthin sample	57	87.5%	43 min	1.75%	A
Republic Airways	1,761	80.9%	79 min	3.18%	B−
JetBlue Airways	892	72.8%	74 min	2.58%	C
American Airlines	2,246	71.4%	82 min	2.89%	C

Republic Airways cancels 3.2% of what it schedules here, the highest in the table. A cancelled flight never appears in an on-time rate, so read that column alongside the punctuality one rather than after it.

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 32 points, against 10 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.

5am–8am785 flights91.3%
8am–11am1,161 flights85.7%
11am–2pm786 flights78.6%
2pm–5pm749 flights63.6%
5pm–8pm1,075 flights59.3%
8pm–5am400 flights69.5%

Scale runs 50% to 95%. Rows with fewer than 30 flights show a dash.

The 5pm–8pm window is where this operation falls apart: 59.3% on time, against 91.3% for the 5am–8am slot. By evening the aircraft flying these rotations have absorbed a full day of small delays and there is no slack left to recover in. The 8am–11am window is the busiest, with 1,161 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.

Darker means more delays. Figures are on-time percentages.February best, September worst

Delays peak in September, when the on-time rate falls to 60.7%. February is the strongest month at 83.4%. Moving a flexible trip across that boundary buys 23 points. October was the busiest month here, with 462 flights.

Across the week, Saturday is the strongest day at 82.7% on time and Sunday the weakest at 69.9%. 13 points is a smaller lever than departure hour, but it is free.

Delay causes

Why this route gets delayed

Carriers report a reason for every delay minute they cause, in five DOT categories. The split below is by minutes, not by number of flights, so a handful of very long weather delays weighs as much as many short ones. It covers 95,000 reported delay minutes.

Late-arriving aircraft
41%
National Airspace System
31%
Carrier
23%
Extreme weather
5%
Security
0%

41% 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 95,000 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 94,573 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 91.3% on time here.

Cancellations run at 2.93%, against 1.81% nationally. That is roughly one flight in 30 cancelled outright. A cancelled flight is invisible in every on-time figure on this page, so the punctuality numbers above describe only the flights that actually operated.

Connections and stage length

What a delay here actually costs

For anyone connecting, the number to weigh is not the on-time rate but the tail behind it. 12.0% of arrivals land a full hour or more behind schedule, against 8.1% nationally. A 45-minute layover does not survive that, and no amount of walking quickly changes it. Ninety minutes is the honest minimum here, and two hours if the onward flight is on a separate ticket.

At 280 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 runs 76.5% on time across 4,961 flights, within about a point of this direction. The two legs are scored separately because they usually differ; on this city pair they happen not to.

The sample behind these figures is 4,956 flights, enough that the headline rate is stable to within roughly a point. The hour-block and month splits divide that further, so read the thinner bars with more caution than the headline.

What to do with this

Booking this route

Put together: the delay figures matter less here than the 2.93% cancellation rate. A late arrival costs you a little over an hour; a cancelled flight costs you the day. Book the 5am–8am departure so there is still a schedule behind you if it goes wrong, and treat a same-day connection as optimistic. 4,811 completed flights over 12 months sit behind that.

Common questions

PHL to BOS questions

How often is PHL to BOS delayed?

About one flight in four arrive at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 24.8% of the 4,956 flights in this analysis, against 22.4% nationally. Delayed flights are late by a little over an hour on average.

Which airline is most reliable on PHL to BOS?

Republic Airways leads at 80.9% on time across 1,761 flights. American Airlines is at the other end on 71.4%, a gap of 10 points. Sample size matters as much as the percentage: a rate built from a few hundred flights moves around far more than one built from ten thousand.

What time of day has the fewest delays on PHL to BOS?

The 5am–8am departure window is the strongest at 91.3% on time. The 5pm–8pm window is the weakest at 59.3%, 32 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 September delays on PHL to BOS?

September is the weakest month at 60.7% on time, compared with 83.4% in February. 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.

Where to go next

Direction matters. PHL to BOS and BOS to PHL are scored separately because they are separate operations, with different departure banks and different aircraft. Compare the return leg.

Source: US DOT Bureau of Transportation Statistics, on-time performance data, July 2025 to June 2026. Updated monthly. How this data is collected.

Key figures