Another data point: arriving from the UK from LCY this morning (Monday 20 June ) after a horrible experience in Heathrow T3 where a late arrival of DL3 and the need to go through security there again made me and at least a dozen others made me miss my connection to AMS. Bus drop at D. Immigration from D again seems to be open, but they were stopping people before the escalators in some square area indicated with liners - I had the impression at least 50-75 people waiting there. I quickly looked at the non-Schengen-Schengen immigration and long queues there too. I then recalled there is another way out near the E-gates, there you could go directly down to the passport control area, and that looked as on the picture below. They had the electronic passport check boots closed 'since the duty officer has to have lunch too' as the one poor support person managing the crowd explained (it was 11.30 at that moment). The line for EU passports took me 20-30 minutes. I estimate the line for non-EU double that time. Due to 1-2 very irritated persons not a nice atmosphere too. Luckily the KMAR checking my pass was in good spirits.
Anyone considering to visit Amsterdam during a 4-5 hour stopover should be aware of this. If lines are so long, best stay airside.
Heathrow experience here,
Status of Air France-KLM at LHR Terminal 4, post 16
