Carrier route record

DLBOS→PHX

Delta Air Lines · Boston to Phoenix

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 BOS to PHX sits in the middle of the pack with a C. About seven flights in ten arrive on time by the DOT's definition, 9 points worse than the national rate of 77.6%. The late ones land about an hour behind schedule. That rests on 428 flights, with a median arrival right on schedule.

The national on-time rate over the same period is 77.6%, so Delta on BOS to PHX runs 9 points behind the country as a whole. Across a thousand flights that is about 85 extra late arrivals.

On time

69.1%

Arrivals under 15 minutes late, of 417 completed flights

Avg delay

57 min

Across delayed arrivals only, not all flights

Cancelled

1.87%

National rate is 1.81%

Whole route

76.7%

Every carrier on BOS to PHX, 2,024 flights

These figures cover 428 flights between July 2025 and June 2026. Beyond the headline rate, 8.2% 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 BOS to PHX

Delta flew 428 of the 2,024 flights on BOS to PHX, about 21% of it. Its 69.1% on time is 8 points worse than the route as a whole, which runs 76.7%. Ranked by on-time rate it is last of three carriers on the route, where the range runs from American at 79.9% to Delta at 69.1%. 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 BOS to PHX
Airline	Flights	On time	Avg delay	Cancelled	Grade
American Airlines	1,316	79.9%	77 min	1.60%	B
JetBlue Airwaysthin sample	280	73.0%	69 min	2.14%	C
Delta Air Lines (this page)	428	69.1%	57 min	1.87%	C

Flight by flight

Delta flight numbers on BOS to PHX

DL 51417:5568.3% · 358 flights

Departure window

When Delta runs best on this route

Departure time is the single lever a traveller controls, and it moves the odds more than most people expect. Each bar below is the on-time rate for flights scheduled to leave inside that window, across 428 flights.

5am–8am—
8am–11am212 flights73.9%
11am–2pm1 flights—
2pm–5pm—
5pm–8pm215 flights64.6%
8pm–5am—

Scale runs 55% to 80%. Rows with fewer than 30 flights show a dash.

The 5pm–8pm window is where this operation falls apart: 64.6% on time, against 73.9% for the 8am–11am 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 5pm–8pm window is the busiest, with 215 flights scheduled in it.

Across the year

Delta on BOS to PHX through the year

Darker means more delays. Figures are on-time percentages.March best, December worst

December is the weak month at 41.0% on time, against 95.9% in March. Winter delays cluster: a single storm system can account for most of a month's shortfall, so an average December hides both very good weeks and genuinely unflyable days. March was the busiest month here, with 49 flights.

Across the week, Monday is the strongest day at 73.0% on time and Tuesday the weakest at 64.8%. 8 points is a smaller lever than departure hour, but it is free.

Delay causes

Why Delta runs late on this route

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 7,293 reported delay minutes.

Late-arriving aircraft
36%
National Airspace System
33%
Carrier
27%
Extreme weather
5%

36% 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 7,293 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 7,293 reported delay minutes.

33% of delay minutes are charged to the National Airspace System: air traffic volume, runway configuration, ground stops. No carrier can price its way out of that, which is why airport choice moves the number here more than carrier choice does. That is 2,387 minutes out of 7,293, against a national NAS share of 21%.

Cancellations sit at 1.87% against a national 1.81%, which is ordinary. Diversions add another 0.70%.

Connections and stage length

What a delay here costs

8.2% of arrivals land an hour or more late, close to the national 8.1%. That is the figure that decides a connection, and it says a 60 to 75 minute layover is reasonable here while anything under 45 minutes is a bet. Most delays on this route last about an hour, which a normal layover absorbs.

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 77.3% on time across 428 flights, 8 points above 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 BOS to PHX

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 69.1% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 417 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