Cheapest Time to Book Flights From the UK (2026): Booking Windows, Months & Days Explained

The cheapest time to book flights from the UK is not one magic day — it is a booking window that changes by trip type, layered over the cheapest months to fly. Here is the 2026 playbook: when to book short-haul vs long-haul, which months are cheapest, and how to dodge the school-holiday traps.