V-Flyer

I’ve been tracking VS73 vs V91; as the departure times are close.
Last week on a few days the flights only averaged 7hr40, and flew really fast.
Where the last few days, even with departing 20 minutes late, the flights are only arriving 10-15 minutes before scheduled arrival. Where normally they make up the delay and then some.
Today both were filed to fly around 520kts, but are only cruising at 430 kts.

Like Vs73-
13 Nov - departed 10:49 (i/o 10.25) landed 13.53pm i/o 14.40pm. 8hr 04 min.

14 Nov - departed 11:14 (i/o 10.25) landed 14.030pm i/o 14.40pm. 7hr 49 min.

15 Nov- departed 10:59 (i/o 10.25) landed 13.32 i/o 14.40pm. 7hr 33 min.

Yet the last 3 days roughly departing at 10.50M but only landing very close to scheduled landing of 14.40pm. (Today - departed 10.54am but only scheduled to land at 14.33pm - 7 minutes before scheduled landing).

Is this to do with weather or shutdown? Just hope on my Vs73 flight they land well before Vs91 due to immigration ;)

It will be weather / season related as west-bound flights are generally slower over the winter months due to the jet stream creating stronger headwinds. The flip side of the coin is that the east-bound flights home should be quicker though.

Thank you. I figured to do with weather.
Perhaps also to do with airspace as well, a lot of flights from LHR and Europe are heading up North as far as Glasgow before turning to Ireland.

Maybe a bit of both as I think you're right that it's also possible that the gradual unwinding of Domestic flight restrictions from 14th November onwards of the US Airport flight restrictions caused by their Government shutdown is forcing them to occasionally ask incoming International flights to stick closer to their slot times (so prompting a slower cruise speed to match up with landing slot).....so it could remain patchy for a few more days at some airports.