How flight price alerts work (and their limits)

A flight price alert is a saved search that a service re-checks for you. You describe the trip and the price you want to pay. The service looks up fares on a schedule and sends you a message when a matching fare is at or below your target. It saves you from searching by hand every day, but it has limits: prices change between checks, the prices it sees are often recently cached rather than live, and it cannot hold a seat or guarantee a fare.

This guide explains how alerts work in general, how Trigger does it specifically, and what to keep in mind.

The basic idea

Every flight price alert has three parts:

• A search. Where you are flying from and to, the dates, cabin, number of passengers and any filters such as maximum stops.
• A target. The price at which you want to hear about it.
• A schedule. How often the search is repeated and how you are notified.

When a check finds a fare that matches your search and is at or below your target, you get an alert. You then decide whether to book.

Where the prices come from

Alert services do not usually connect to every airline directly. They get prices from travel data providers that collect fares from airlines and travel agencies. Many of these providers keep a cache, which is a store of prices that travellers and systems have recently seen.

Trigger uses official data partners only. Flight prices come from the Travelpayouts network, specifically Aviasales. For some hits, Trigger also uses Google travel results through SerpApi to confirm the price live before emailing. Trigger does not scrape airline or travel websites.

Cached prices are useful because they cover many routes and dates quickly, but they can be a few hours to around two days old. That is why the price on the booking site can be different from the one in your alert. Read more in cached vs live travel prices.

How often Trigger checks

Fares move faster as departure approaches, so Trigger checks more often for trips that are coming up soon:

• about every 12 hours for trips more than 60 days away
• every 6 hours for trips 15 to 60 days away
• every 3 hours for trips 4 to 14 days away
• every hour for trips 3 days away or less

If the last price seen is within 10% of your target, Trigger moves the alert up one tier and checks it more often. When several people have set up exactly the same search, Trigger checks it once and uses the result for all of them, which keeps things efficient.

When Trigger emails you

Too many alerts become noise, so Trigger follows simple rules:

1. You get one email the first time the price is at or below your target.
2. After that, you only get another email if the price drops at least 5% below the last price you were emailed about.
3. Each alert sends at most one email per 24 hours.

Every email has a one-click unsubscribe link. Alerts end automatically on the departure date, so you will not keep getting messages about a trip that has passed.

The limits you should know about

Price alerts are helpful, but they are not magic. Being clear about the limits helps you use them well.

• Prices can change between checks. A fare may drop and rise again before the next check. An alert can miss a short-lived dip.
• Cached prices can be out of date. The price in an alert is a price that was recently seen. When you click through, the booking site shows the live price, which may be higher or lower.
• Seats can sell out. A low fare often applies to only a few seats. By the time you open the email, they may be gone.
• No price guarantee. An alert service does not sell tickets and cannot hold a fare. Trigger cannot guarantee availability or price.
• Coverage is not complete. No data source includes every airline, fare and booking site. Some fares, such as those sold only directly by certain airlines, may not appear.
• Total cost can differ. Baggage, seat selection and payment fees vary between sites. Always check the full price before paying.

How to use alerts well

• Set a realistic target. A target that is far below anything seen on the route may never trigger. Start with a price a little below the normal range. See how to set a realistic target price.
• Allow some flexibility. Flexible dates and accepting a stop widen the search and make a hit more likely. See how flexible dates help.
• Act fairly quickly. When an alert arrives, check the booking site soon.
• Read the fare rules. Make sure the ticket suits you before you pay.
• Keep a deadline. Decide when you will book anyway if the target is not reached.

How to set a Trigger for it

1. Open flights and enter your route, trip type (one-way or return), dates, cabin and passengers.
2. Choose date flexibility from 0 to 3 days and the maximum number of stops.
3. Enter your target price and create the alert. You can have up to 10 active alerts, free.
4. Trigger re-checks on the schedule above and emails you as soon as the price is at or below your target, with a link to book on a trusted partner site.

For more detail, see how it works and the FAQ.