Flight number record
YX 5631
Republic Airways · Indianapolis to Boston
- Route
- IND → BOS
- Departs
- 06:00
- Flights
- 365
- Period
- September 2025 to August 2026
Historical statistics for September 2025 to August 2026, not live status. For today’s YX 5631, check with Republic Airways. Republic Airways flies under contract for larger airlines, so a ticket for this flight may show a different airline code and number.
YX 5631 earns an A. Nearly every flight arrives inside the 15-minute window the DOT uses to define an on-time arrival, which puts it 16 points better than the national rate of 77.3%. When something does go wrong the average delay runs roughly 40 minutes. That rests on 365 flights, with a median arrival 18 minutes early.
Set against the rest of the country, YX 5631's record is 16 points better than the US average of 77.3%. That gap is worth roughly 163 fewer late arrivals for every thousand flights.
Key figures
On time
93.6%
Arrivals under 15 minutes late, of 359 completed flights
Avg delay
42 min
Across delayed arrivals only, not all flights
Cancelled
1.64%
National rate is 1.89%
1 hour+ late
1.1%
National rate is 8.3%
These figures cover 365 flights between September 2025 and August 2026. The median arrival is 18 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.
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Schedule
When YX 5631 flies
YX 5631 flies IND to BOS without a single fixed slot. Its most common scheduled departure was 06:00, used on 85 of 365 flights, with 06:40 (59 flights) and 06:15 (48 flights) next.
- Departs 06:0085 flights23.3%
- Departs 06:4059 flights16.2%
- Departs 06:1548 flights13.2%
Scale runs 0% to 100%.
Share of scheduled departures at each local time. Times used on fewer than one flight in ten are not listed.
A 06:00 departure sits in the 5am–8am window. Across every US flight scheduled in that window the on-time rate is 89.3%, and YX 5631 runs 4 points better at 93.6%. Early departures usually start with an aircraft that has not flown yet that day, which is most of why the window does well.
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Against the route
YX 5631 next to IND to BOS
Every carrier on IND to BOS combined arrived on time 78.8% of the time across 2,025 flights, so YX 5631 is 15 points ahead of it. Republic flew 1,975 flights on the same city pair under all its flight numbers, including this one, and those ran 78.9% on time. Across its whole network Republic Airways managed 78.1%, which this flight beats by 16 points.
| Compared with | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| YX 5631 | 365 | 93.6% | 42 min | 1.64% | A |
| All Republic Airways on IND–BOS | 1,975 | 78.9% | 71 min | 2.78% | B |
| All carriers on IND–BOS | 2,025 | 78.8% | 71 min | 2.77% | B |
| Republic Airways, whole network | 364,452 | 78.1% | 74 min | 4.55% | B− |
Across the year
YX 5631 quarter by quarter
YX 5631 did not run the same all year. Its best quarter was Apr–Jun 2026 at 98.9% on time and its weakest Jan–Mar 2026 at 86.9%, a swing of 12 points on roughly 73 flights a quarter. The twelve-month rate averages over that, so if you are flying in a weak quarter the quarter's own figure is the better guide.
- Jul–Sep 202530 flights96.7%
- Oct–Dec 202592 flights90.2%
- Jan–Mar 202690 flights86.9%
- Apr–Jun 202691 flights98.9%
- Jul–Sep 202662 flights98.4%
Scale runs 80% to 100%.
By weekday, YX 5631 did best on Sunday at 100.0% on time and worst on Monday at 82.4%. Each day rests on about 52 flights, so a gap of 18 points is worth noticing but could still narrow in another year.
Arrival by arrival
How late YX 5631 runs when it is late
YX 5631 often beats the schedule: 214 of 359 completed flights, 60%, arrived 15 minutes or more early. The 23 late arrivals split 11 under half an hour, 8 between 30 and 60 minutes, and 4 an hour or more.
- 15+ min early214 flights59.6%
- Within 15 min122 flights34.0%
- 15–29 min late11 flights3.1%
- 30–59 min late8 flights2.2%
- 1–2 hours late3 flights0.8%
- 2+ hours late1 flights0.3%
Scale runs 0% to 100%.
Share of 359 completed flights by arrival against schedule.
Only 16 of 359 completed flights left 15 minutes late or more, too few to say how often the time is made up.
The worst days
Worst days for YX 5631
The latest arrival of the period was on 27 January 2026, 3 hours 3 minutes behind schedule; most of its delay minutes were filed as national airspace system delay. The five worst days are spread across January, December, August and February, with no single month standing out.
| Date | Arrived late by | Largest filed cause |
|---|---|---|
| 27 January 2026 | 3 hours 3 minutes | National Airspace System |
| 12 December 2025 | 1 hour 42 minutes | Extreme weather |
| 21 August 2026 | 1 hour 23 minutes | Carrier |
| 9 February 2026 | 1 hour 3 minutes | Carrier |
| 19 January 2026 | 55 minutes | National Airspace System |
Delay causes
Why YX 5631 runs late
National Airspace System accounts for 57% of the 969 delay minutes carriers reported here, and the remaining four split what is left.
- 57%National Airspace System
- 35%Carrier
- 8%Extreme weather
The largest share of delay minutes, 35%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. It accounts for 341 of the 969 delay minutes reported here. The split is drawn from 969 delay minutes reported on YX 5631.
Cancellations sit at 1.64% against a national 1.89%, which is ordinary. Diversions add another 0.00%.
Connections and routes
What a delay on this flight costs
Badly late arrivals are rare here: only 1.1% land an hour or more behind schedule, against 8.3% 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.
The 818 miles between these two airports put this in the middle of the US network, around two and a half to three hours of block time. That is enough cruise to absorb a ten-minute late pushback and not enough to absorb thirty.
Every one of the 365 flights under YX 5631 in the data flew IND to BOS. The number was not reused on any other city pair, which makes this a clean record of one route.
One caution: this is a thin sample. 365 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 YX 5631
For a booking, read YX 5631 as 93.6% on time with 1.64% cancelled over 365 flights. Those are rates from the past twelve months, not a forecast for any particular day.
Related
Where to go next
- IND to BOS, every carrier and departure
- BOS to IND, the return direction
- Republic Airways 4716 on the same route88.2%
- Republic Airways 4726 on the same route68.0%
- Indianapolis International (IND) delay statistics
- Boston Logan International (BOS) delay statistics
- Republic Airways on-time record
- Every Republic Airways flight number with a record
- The most and least reliable flight numbers in the US
- Worst months to fly in the US, ranked by the data
A flight number here means Republic Airways’s own number as it reports to the DOT. How the figures are computed is on the methodology page.
Source: US DOT Bureau of Transportation Statistics, on-time performance data, September 2025 to August 2026. Last updated ; recomputed monthly. How this data is collected.