Jetstream all the way. I was on a Delta (I know.....) flight from JFK-SFO on the afternoon of the 18th and we were bucking serious headwinds most of the way. The highest I saw were 186 MPH headwinds cutting our groundspeed down considerably. We kept climbing and got up to 36K I believe (34K for sure, I was a little groggy....) and could not shake the jetstream.