From Yahoo Travel: what day of the week to buy airplane tickets for the best deal. Short version: round trip domestic airfares average about $430 on weekends and about $500 on weekdays, so buy on the weekend. The Yahoo piece is, in turn, a condensation of this piece from the Wall Street Journal. The WSJ piece acknowledges that a portion of this is because price-insensitive business travelers buy on weekdays and price-sensitive leisure travelers buy on weekends.
(Are business travelers really price insensitive? Sure doesn’t seem like it where I work, and lots of places have policies that basically require the employee to book at the lowest price unless they jump through a whole bunch of bureaucratic hoops. Whereas if I’m an individual buying a ticket, I can pay a little more for the more favorable schedule without asking anyone. But I digress…)
Seems to me that the big elephant in the room is that business travelers travel on different routes than leisure travelers. And if I’m trying to buy plane tickets for myself and hoping to be able to time this purchase, I don’t care what prices I could get on other tickets being bought by other people on the same day as me.
We could reproduce the phenomenon these articles are showing as follows. Imagine an airline with two routes. Say that tickets on route A, a business-heavy route, cost 600 dollars regardless of the day, and on route B, a leisure-heavy route cost 300 dollars. On weekdays, two-thirds of tickets purchased are on A and the average price is 500; on weekends only half of tickets are on A and the average price is 450. This whole thing may be a less severe form of Simpson’s paradox – I’m saying it’s less severe because a true Simpson’s paradox would have it actually being more expensive to buy tickets on the weekend for any given route.
It’s not impossible that it’s actually cheaper to buy tickets for a given route on the weekend – but looking at simple averages won’t prove it.
God plays dice 
Basically what you’re saying is anyone can say anything unless they show the data.
Got it! Thanks a lot again for henlipg me out!
Bonjour Eric,Je vais attendre ton âme avec impatience, il reste encore pas mal de place ici !A bientôt pour la suite de l'aventure."E"
Are they talking about when to BUY or when to FLY? In my experience it matters a lot when you fly (the 430 to 500 ratio seems like a smaller difference than I’d have thought). I think the explanation that business people are (relatively) price sensitive means “we need to fly on day A so we’ll buy the cheapest ticket on that day A even if the flights on day B are a lot cheaper” rather than “we’ll buy the most expensive tickets on day A because we don’t care too much about the price”