Airline crews are still slightly confused. On a recent flight I was given the white form to fill out which when presented to the immigration guy was promptly torn up as I have completed ESTA. Took less than 20 mins from parking to being on the inter-terminal train having completed the usual formalities & handing baggage back for onward connecting flight. Took 45 mins to get back into the UK thanks to T1 at LHR not having a UK nationals only line + only 4 manned booths at 8:30am.