> land at Heathrow you don't go pass passport control if you change onto another international flight. You go through security and then into the departure lounge.
replyThis requires a Direct Airside Transit visa, unless you are a citizen of one of the exempt countries or have a visa/residence permit from certain countries (US, Canada, Australia, New Zealand, Ireland, Schengen). Applying for this visa involves going to the local visa processing centre, so it is not an online or on-arrival process, and takes around 3 weeks.
majority of countries don't need an airside transit, from Bhutan to Kazakhstan, Indonesia to Venezuela, hell even North Korea.
replyA US citizen flying New York to London to Egypt does not need to pay £20 for an ETA "visa waiver" to transfer in London. A UK citizen flying London to New York to Lima does need to pay for an ESTA