The price alerts emails are intended as a guide, and are based on a snapshot in time on the day it was sent for a single adult travelling. Flight availability, meanwhile, is live and can change very rapidly based on traveller demand and airline pricing structures.
At times, this can result a flight that you have an alert set up for no longer available at the emailed price, or at all. This may be particularly noticeable when there has been any delay between receiving the price alert email and clicking the link, but can sometimes even change within minutes or even seconds of the alert going out.
Another situation which could result in a price difference is where your original search was for multiple passengers. Price Alerts check for single adult prices only, but we do remember your passenger selection so when you click through you will see prices based on those passengers.
We still hope that the majority of the time there is no significant change, and the feature is still useful for finding the best prices for your chosen route. Of course very occasionally it might be that we have a technical problem leading to an incorrect price. If you feel this might be the case we would be very grateful if you could provide us with the details of your search (dates, airports, flight times, number of passengers, airline and travel agent, if applicable). We can then try to investigate the issue.