Carrier route record

DLPHX→BOS

Delta Air Lines · Phoenix to Boston

Flights: 428
Period: July 2025 to June 2026
Share of route: 21%
Carriers: 3

Historical statistics for July 2025 to June 2026, not live status. For today’s flights, check with Delta Air Lines.

Delta on PHX to BOS lands a B, level with the national rate of 77.6%. Roughly one flight in four arrives 15 minutes late or worse, and those flights are late by close to two hours on average. That is a workable record, not a spotless one. That rests on 428 flights, with a median arrival 5 minutes early.

The US average over the same twelve months is 77.6%, so there is little to separate Delta on PHX to BOS from the country as a whole. The variation that matters here is internal: which carrier, and what time of day.

On time

77.3%

Arrivals under 15 minutes late, of 418 completed flights

Avg delay

106 min

Across delayed arrivals only, not all flights

Cancelled

2.34%

National rate is 1.81%

Whole route

77.3%

Every carrier on PHX to BOS, 2,022 flights

These figures cover 428 flights between July 2025 and June 2026. Beyond the headline rate, 9.3% 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

Delta against every carrier on PHX to BOS

Delta flew 428 of the 2,022 flights on PHX to BOS, about 21% of it. Its 77.3% on time is about level with the route as a whole at 77.3%. Ranked by on-time rate it is number two of three carriers on the route, where the range runs from American at 78.5% to JetBlue at 71.4%. One of those carriers flew fewer than 365 flights here, so treat their positions as rough.

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.

On-time performance by carrier on PHX to BOS
Airline	Flights	On time	Avg delay	Cancelled	Grade
American Airlines	1,314	78.5%	70 min	1.60%	B
Delta Air Lines (this page)	428	77.3%	106 min	2.34%	B
JetBlue Airwaysthin sample	280	71.4%	79 min	2.14%	C

Departure window

When Delta runs best on this route

Departure time matters more here than the choice of carrier. The gap between the best and worst window is 15 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–8am—
8am–11am—
11am–2pm196 flights69.3%
2pm–5pm16 flights—
5pm–8pm—
8pm–5am216 flights84.0%

Scale runs 60% to 90%. Rows with fewer than 30 flights show a dash.

The weak window here is the middle of the day, not the evening: 11am–2pm runs 69.3% on time against 84.0% for 8pm–5am. That shape usually means a departure bank rather than an accumulating delay, so the recovery later in the afternoon is real rather than noise. The 8pm–5am window is the busiest, with 216 flights scheduled in it.

Across the year

Delta on PHX to BOS through the year

Darker means more delays. Figures are on-time percentages.May best, October worst

May is the best month on the calendar at 94.3% on time. Shoulder season thins the schedule and takes the summer weather with it, and the operation gets its margin back. March was the busiest month here, with 49 flights.

Across the week, Saturday is the strongest day at 88.1% on time and Sunday the weakest at 69.8%. 18 points is a smaller lever than departure hour, but it is free.

Delay causes

Why Delta runs late on this route

One category carries most of the weight here. Carrier accounts for 53% of the 10,000 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.

Carrier
53%
Late-arriving aircraft
23%
National Airspace System
19%
Extreme weather
5%

The largest share of delay minutes, 53%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. Unlike weather, that is a management outcome, and it is the category where the gap between two carriers on the same schedule is genuinely earned. It accounts for 5,295 of the 10,000 delay minutes reported here. The split is drawn from 10,050 reported delay minutes.

Cancellations sit at 2.34% against a national 1.81%, which is ordinary. Diversions add another 0.00%.

Connections and stage length

What a delay here costs

For anyone connecting, the number to weigh is not the on-time rate but the tail behind it. 9.3% 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 2,300 miles this is transcontinental flying, and long routes get a quiet structural advantage. Scheduled block time on a flight this length carries more padding in absolute minutes, so a twenty-minute late departure often still becomes an on-time arrival. Read the on-time rate here as slightly flattering next to a short-haul route with the same operational quality.

The return leg is a different operation and performs like one: it runs 69.1% on time across 428 flights, 8 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 8 points of difference.

One caution: this is a thin sample. 428 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.

What to do with this

Booking Delta on PHX to BOS

Put together: treat all of this as provisional. 428 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 77.3% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 418 completed flights over 12 months sit behind that.

Where to go next

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.

Key figures