In the USA, the FAA permits bringing an empty fuel bottle.
I'm flying between the United Kingdom and Iceland on Icelandair. Can I bring an empty fuel bottle in checked baggage? It does have big "danger" signs on it.
Image from Amazon.
According to Icelandair's website, under Baggage restrictions, "Camping stoves and fuel containers that have contained a flammable liquid fuel, with empty fuel tank and/or fuel container" are "permitted in or as checked baggage", but the "approval of Icelandair is required". This statement is followed by a big button to open a "Contact Icelandair" form.