The best time to book cheap flights is typically 6 to 8 weeks before your departure for domestic travel, and 2 to 5 months ahead for international trips. Tuesdays and Wednesdays often have the lowest fares, and flying midweek or off-season (shoulder months like May or September) helps cut costs. Use price alert tools like Google Flights or Skyscanner to monitor deals and act quickly when prices dip.