Before you book any flights, take a moment to check your nationality against Turkey's visa rules because they vary a lot. Some travellers can enter without a visa for up to 90 days, others need to apply online for an eVisa, and many must go to an embassy for a traditional sticker visa. I almost made the mistake of assuming my passport was fine, but I actually needed a supporting document like a valid Schengen or UK visa. The Turkey Visa Policy page clearly lists visa free countries, eVisa eligible nationalities, and those who need embassy processing. For instance, US and UK passport holders often travel without a visa, but many Asian and African nationals need to apply well in advance. Also, the transit eVisa only works if your final stop is Colombia, Mexico, Panama, or Venezuela. Checking these rules at least two weeks ahead saves you from unnecessary stress at the airport.