Originally Posted by
PETER01
No you don't have to be there at 5.50 am.
I'd check in online at T-24 or shortly thereafter but you can check in right up to 45 mins before departure at Heathrow (1 hour if checking in bags IIRC but I'm not 100% sure of that) but I certainly wouldn't recommend that! It will start to get busy at 0600 but not at the F desk I suspect if you are using that.
The technical deadlines at LHR are 35 minutes to get the Security areas, 45 minutes for check-in including luggage. This is system coded so there's no leeway. If hand baggage only there is leeway in that they can call the gate. Checked luggage isn't an issue at 45 minutes in normal circumstances. If the aircraft is very delayed then these timings can also move.
If it's not a school holiday Friday or Saturday, and you are fully mobile, then checking in one hour beforehand will be fine, so 75 minutes will give you a cushion. So personally I'd be looking to be there around 07:50 hrs given it's a Thursday, but somewhere in the 07:00 to 07:30 hrs would be more than adequate.