Short answer, I suspect, is: School holidays.

Since LH withdrew the FRA-PDX route there's no longer a direct EU-PDX route, AFAIK*. This leaves you a choice of AC J via Toronto or Vancouver and various routes involving other jumping off points e.g. ORD/LAX/SFO/IAH etc.

AC J, seems very difficult to get hold of at the best of times. A quick look at EF for these dates suggests that you might be able to find a seat in Y on AC from LHR.

I'd recommend looking at trying to get an UA/LH/LX flight to LAX/SFO/ORD/LAS(?) if possible and trying to tack on a UA flight to PDX (which will need to be in Y - to avoid triggering F miles for the entire flight).


m.

* There is a UA flight but it's one of those flights where the flight number persists while all the passengers have to change planes (and terminals).