I am travelling to the USA, but going via Heathrow. I catch my first flight from Manchester at approx 6am.
The advice I have usually followed is to arrive at the airport 3+ hours in advance of a long haul flight, 2 hours for short haul and 1.5-2 hours for a domestic flight.
So in my situation, with the domestic being first leg of a long haul journey, how early should I aim to turn up? I will be checking in online first.