When is the busiest period for UK to US?

[Wilton Shagpile]

I'm going standby to the west coast of the US from the UK this summer. Apart from the obvious like US holidays etc. are there any times that I should really avoid like the plague? I know the schools are out and it is going to be generally pretty busy, but it was just in case there were any other things I though think about or any week(s) when it is historically really busy.

It will be either SFO, LAX or SAN..

Also possibly out of somewhere in Europe - AMS, FRA etc....

[Hartington]

It's a bit like asking how long the proverbial piece of string is. It amazes me how one seat can pop up on the busiest flight and how a flight that has been empty for days will suddenly refuse boarding at the last moment. Some of it is due to capacity planning - last minute change in weather can restrict (or improve) the load carrying capability of an aircraft. That said, when travelling as a family of 4 on a large UK airline, (!) I have always looked upon Tuesday and Wednesday as better days. What I've never quite worked out is the relationship between connecting traffic and flight availability. The impression I get is that the 1st flight is early enough that there is little European connecting traffic (although increasingly there is traffic from further east) so those flights tend to be used by locals and the later ones fill up with connecting pax.