Question: what is the best day to buy plane tickets online?
Answer: Shop on Tuesday. Best day to shop: The best time to book a U.S. flight is usually Tuesday at about 3 p.m. eastern time. ... 
Don't Shop too Early or too Late. Careful! ... 
Always Compare Airfare. The golden rule of shopping: Always compare airfares. ... 
Cheapest Days to Fly. ... 
Fly the Cheapest Route. ... 
Book Group Travel One Ticket at a Time.