Before you book any flights, it is essential to check your nationality against Turkey's visa policy because the rules differ significantly depending on where you are from. Some travelers can enter visa free for up to 90 days, while others need to apply online for an eVisa, and many must visit an embassy for a traditional sticker visa. I almost made the mistake of assuming my passport was eligible, but I actually needed a supporting document like a valid Schengen or UK visa to apply. The Turkey Visa Policy page has a full breakdown of visa free countries, eVisa eligible nationalities, and those who require embassy processing. For example, US and UK passport holders can usually travel without a visa, but many Asian and African nationalities need to apply online well in advance. Also keep in mind that the transit eVisa only works if your final destination is Colombia, Mexico, Panama, or Venezuela. Checking these rules at least two weeks before travel saves you from last minute stress at the airport.