If you're traveling on your own, no problem. Just book your tickets. All you have to do is compare prices on an airfare search site to find the cheapest flight available.

But what about when you're traveling with family and friends? Here's where it gets interesting. You could shop the usual way–entering the total number of passengers instead of just one–but doing that might mean you spend more than you have to.

Key Takeaways

  • If you purchase multiple tickets in a single transaction, the price will be the same for each of the tickets.
  • If not enough of the lowest-cost seats are available, you'll pay a higher cost for all of the seats.
  • Buy the tickets one at a time to make sure you get all of the lowest-cost seats available.

Here's a technique that ensures that you'll get the lowest possible fare for every ticket you buy.

The Reservation System Quirk

A quirk in airline reservation systems requires that every ticket purchased in a single reservation (or transaction) be the same price. If there aren't enough of the cheapest-priced tickets available, the system moves up to the next highest level of ticket prices. When it reaches a level that has enough seats available, it offers you the higher price for all of them.

To help make sense of this, it's useful to know that there are about 10 different price points on each flight. There are even multiple price points within economy class. The prices vary depending on when you buy your tickets.

Let's say you're seated in a middle seat in coach and paid $100 for your ticket. To your left is a woman who paid the next lowest fare of $125 and to your right is a fellow who paid the top economy price of $140. (These figures are pulled out of the air for illustration purposes but all are well within the range of possibility.)

When Prices Vary

Now say you took your family of four along on that trip. You buy your tickets in a single transaction as usual. If there are four tickets available at the lowest price, terrific. You got the $400 deal.

But let's say there are only two of the cheapest tickets left. If you buy all four tickets in one transaction, you will not pay $100 + $100 and $125 + $125 for a total of $450. Instead, you will pay $125 for every ticket, for a total of $500.

Remember the system quirk? The system will not split up a group to mix ticket prices because all tickets sold in a single transaction must be sold for the same price. When there are not enough cheaper-priced tickets to match the number of passengers, the reservations system automatically bumps up to a price tier where there are enough same-priced tickets.

This can be avoided, though. All it takes is a few extra minutes of your time.

Purchase Tickets One at a Time

Whichever travel booking site you use, begin by opening two separate flight search pages to your destination:

  • On one page, open a booking for one person.
  • On a second page, open a booking for the total number of people in your party.

If the price offered in the search for a single ticket is cheaper than the per-ticket price offered for the whole party, you know there is at least one cheaper seat available. Buy it, and repeat the process of buying a cheaper ticket one at a time. You may end up buying all the tickets you need, one at a time.

If the price of one ticket rises to the price shown on your group booking page, you can use the group booking page to order the remaining seats you need all at once. Or, change the seat number on the single-ticket search page to buy the remaining tickets at the higher price.

You've just bought all of the tickets at the lowest total price available.

If You Press the Wrong Key

U.S. airlines are required to give you a 24-hour change-your-mind grace period to cancel a reservation in case of an error. Most offer a straight refund within this period. American Airlines’ policy is to allow shoppers to hold a booking for 24 hours (with no price change) before paying for it.

Rick Seaney is the CEO and co-founder of FareCompare.