For international travel in 2026, the primary document remains a valid passport, which most countries require to be valid for at least six months beyond your departure date. You must also carry any necessary visas or electronic authorizations, such as the US ESTA, the UK's new ETA, or the EU's ETIAS. Beyond identity papers, you should have digital or printed copies of your flight itinerary, proof of accommodation, and travel insurance details, as immigration officers often request these to verify your stay. In some regions, vaccination certificates (like Yellow Fever for specific African or South American routes) or proof of sufficient funds (bank statements) are mandatory entry requirements. For domestic flights, a government-issued photo ID is standard, though many countries now accept digital IDs through official government apps. It is highly recommended to store physical photocopies of all these documents in a separate bag and keep high-resolution digital backups in a secure cloud service to ensure you can quickly verify your identity if the originals are lost or stolen.