Welcome to FT!

As far as promotions go.. from years of experience I have noticed you can often do far better on price before or after the fare sale...and fares usually offered during a sale are nothing to write home about. Sometimes UA will advertise a "sale" but in reality all they're doing is announcing fares they've had available all along anyway.

There is no real pattern as to when fare sales are announced... and if you're talking about summer travel it is the peak season and traditionally flights from the US to Europe are quite expensive and there's really no way around it. But with the economy the way it is this year perhaps this summer will be different if it gets closer and bookings are light. No way to know. If I were you I'd keep checking your desired dates every couple days.