Hello,
first time to land in IAD. Is 3.5 hours enough to clear immig, pick up luggage, re-check in
-business class ANA arrival and business class United departure
-US passport and have MPC
-arriving 9th January at 9:10am. Departing flight at 12:40pm

Thank you!

All on one ticket?

different ticket.

There have been some reports suggesting that ANA might be willing to through-check your bag across separate NH => UA tickets. When checking in with NH, I would show the agent a printout of your UA ticket, and ask about through-checking. You'd still have to claim your bag and undergo Customs inspection at IAD, but you could then just drop your through-checked bag at the bag drop past Customs, instead of having to stop at a UA ticket counter. That would save you a few minutes.

Even without through-checking, I would think that 3.5 hours is enough time to make your self-transfer, but I do not have personal experience arriving IAD from abroad.

Good luck!

3.5 hrs for US passport at early AM non-rush hour arrival at IAD should be more than enough.

Thank you so much for the replies, and the suggestion to ask to check through.

You get in at about 9am which is not a busy time for international at IAD. Should be OK in my mind.

Should be plenty of time, absent arrival flight delay obviously.

Not sure of your lounge eligibility, but note that United flights depart mostly in the C and D concourses, which are very 20th century and the United lounges are so-so at best. Better Star Alliance lounges are in the B concourse, though you'll need some time for the round trip travel (though perhaps some walking would be welcome in-between flights).

That's plenty of time. International morning arrivals around your arrival time consist of the following flights:
In this particular order between 8am and 10am.
- Ethiopian A350-1000 - 395 pax
- Emirates A380 - 489 pax
- Qatar A350-900 - 283 pax
- Etihad B787-9 - 290 pax
- ANA B787-9(or -8 on some days) - 246 pax
- Korean Air B777-300 - 277 pax

Between 5am and 7am you have United international arrival bank. But all flights should clear the customs way before any of the other intl flights arrive.
6am Lagos B787-8
6am Cape Town B787-9
6am Guatemala City B737-8
6am Sao Paulo B767-400
6:30am San Salvador B737-8

Copa, Avianca and Volaris arrive between 12 midnight and 5am, so no jam at the customs.

Morning is the only time at Dulles where you shouldn't worry about making your intl to domestic connection

Wow thank you so much for the encycopedic answer! Appreciate it.

What ended up happening:

Landed at 9:17.
Cleared immig and customs by 9:37
Bag recheck
Cleared domestic security by 9:53

The big bummer is that United does not allow lounge access even with biz ticket IAD-BOS. Quite shocked.