Is there a best day to get the lowest price on a flight?

Many travelers think the magic day is Tuesday, long lauded by travel deal sites and various publications, including this one, for its fare sales. Other travelers may have heard pundits declare Wednesday the ideal day. In December, Expedia and the Airlines Reporting Corporation, which processes ticket transactions for airlines and travel agencies, announced that weekends are the new best time.

But is there really a preferred day to buy?

“I just want to drive a stake through the heart of that myth,” said George Hobica, the founder of the deal alert site Airfarewatchdog.com, who has been looking at airfares on popular routes every day for more than 20 years, with the rare exception of a vacation where he doesn’t have Internet access.

There are too many variables at play for there to be a universally ideal day to buy an airline ticket. Price depends on a variety of factors, including the route; the level of competition on the route; surrounding holidays and events (like a convention or the Super Bowl); and the days of the week you plan to fly. During a single week in March, for example, a recent search for a round-trip flight between New York and Miami turned up ticket prices as low as $174 and as high as $314. Besides, nowadays we have fare calendars at our fingertips and websites such as Kayak and Travelzoo that alert us to low fares and sales — and those sales don’t always take place on the same day of the week.

Mr. Hobica pointed out, for instance, that on a recent Thursday, Virgin Atlantic lowered nonstop winter flights to Heathrow Airport in London from John F. Kennedy International Airport or Newark Liberty International Airport to about $504 round-trip. Economy fares had been running $900, Mr. Hobica said, then $800, then they went back up, and after that they dipped to around $680.