Want cheap flights? Book early: Analysis by travel search engine finds the best time to buy tickets for destinations across the globe Travel experts analysed millions of flight prices to find when it’s cheapest to book – and found the best deals to Europe are one or two months in advance whereas a trip to Dubai must be booked nine months ahead. Travel search engine Kayak.co.uk released data for the ten most popular European destinations for this year, plus the top ten international destinations.