Can A green card holder seaman sign-off from a ship in Gibraltar and come back home in USA via Heathrow Airport London UK?

Yes, a green card holder seaman can sign off from a ship in Gibraltar and travel back to the USA via Heathrow Airport in London. They should ensure they have the necessary travel documents, including a valid green card and a passport. It's advisable to check any transit visa requirements for the UK, as they may vary depending on nationality. Additionally, they should confirm any re-entry requirements into the US before traveling.