Previously, UK passports could extend up to nine months of validity from an old passport to a new one.

However, the EU now mandates that passports must have been issued within the last 10 years to be considered valid for entry.

Nathan Barnes, a 31-year-old paramedic from Norwich, experienced this firsthand when he was denied boarding for his flight to France. Despite successfully checking in online and passing through security, his passport, issued over 10 years ago, led to his travel plans being abruptly canceled.

This rule affects travel to all EU countries, plus Iceland, Norway, Liechtenstein, and Switzerland (excluding Ireland), requiring passports to be issued less than 10 years before the departure date and valid for at least three months after the intended return date.

For passports issued prior to September 2018, the potential for extra validity up to 10 years and nine months exists, misleading some travelers about their document's eligibility for EU travel.

Travelers are urged to check their passport's issue date if planning to visit affected countries and consider renewal options if necessary, including emergency appointments for urgent cases. Regular renewals may take up to three weeks through HM Passport Office.

Experts like Rory Boland from Which? and Simon Calder from the Independent emphasize the importance of verifying passport validity well in advance of travel dates to avoid disrupted plans. Airlines, despite offering reminders, stress the traveler's responsibility in ensuring passport compliance.

With a significant number of travelers potentially affected, awareness and timely checks are crucial to prevent being turned away and facing financial losses. Also, note that passport fees are set to increase from 11 April, with a standard adult renewal costing £88.50.