I just booked a cheap 300€ roundtrip ticket on NWA from Frankfurt to Boston two weeks from now. Nice, however the routing is
FRA-Detroit-BOS, BOS-Detroit-FRA.

Outbound I've got 70min in Detroit to change planes. On the return trip, it's only 45min.

Is this even possible? The tickets are confirmed, so I believe it could work?

Sh.., of course it should read:

45 min transfer time in Detroit - possible?

Sorry!

I think you should be ok. It is easier to leave the country than it is to enter it.

If the company offered that connection for you, they have to be prepared to give you a later trip for free if you miss the connection. So I would trust them to know what they're doing...

Yes, you will be fine. All the NWA gates in Detroit are together. Too bad you have to go through Detroit though. This adds a lot of time to your journey.

Have a good idea what would happen to you if the inbound flight is delayed -- bad weather can eat up that 45 min. quickly. I'd have in hand the schedule of later flights to BOS and also to FRA and if you're late, FIRST try calling NWA WHILE you're standing in line to talk to an agent. Much of the time, they can do better for you over the phone than they can on the ground -- and you've effectly beaten the other people in line to the punch.

(by "inbound" I mean whatever flight is taking you to Detroit -- in either direction)

Thanks, I'll take their phone numbers with me!!

I don't know DTW airport, but here is my take on the situation:

FRA-DTW-BOS - 70 minutes - it may/may not work. You need to go through immigration, collect luggage(if you have any checked luggage), customs, drop off luggage outside of customs, (possibly) change terminals, go through security, get to the domestic gate. NWA will put you on a later flight if you don't make it, so don't worry, but be prepared.

BOS-DTW-FRA - 45 minutes - no problems as long as your first segment is on time.

Just a broader comment here: I'm guessing the "penalty" for missing connections is going to become yet more punitive as the number of flights is reduced and flights are overbooked on top of being overbooked. You may be booked on a "later" flight if you miss the connection, but that later flight might not be the same day, or even the next day in some cases.

More reason to book yourself with plenty of leeway, but even then, the unwritten (and sometimes written) rules of priority may keep you grounded.

When entering or leaving the country I always try to leave at least 90 minutes between flights. I'd much rather plan for a 2 hour longer trip to begin with, than perhaps a day or two delay, particularly when most flights are required to be boarded 30 minutes prior to take off. You'll need luck on your side to make both connections. Are the flights w/the same airline or are you changing to differing airlines ?

Both flights are with the same airline. I booked FRA-BOS-FRA and that route came up. So I guess NWA know what they are doing?