Passengers looking for cheap airfares are advised to book flights at least three weeks ahead of travel and buy their tickets on a weekend. That's the advice from the 2019 Travel Pricing Outlook compiled by air travel intelligence firm  Airlines Reporting Corporation and online giant Expedia, although it comes with some caveats. The weekend thing doesn’t work in New Zealand and, even with an extensive analysis of traveler data from the two global groups, the report says it is impossible to actually guarantee when you will find the lowest prices. Setting airfares is an arcane business controlled by sophisticated computer algorithms but the 2019 Travel Pricing Outlook looks at outcomes in an attempt to discern trends. It’s no great surprise that they found that average airfares for economy and premium cabins in most parts of the world tend to rise as the departure date gets closer. “Waiting to book at the last minute can be an expensive gamble,’’ they said. “Booking three weeks ahead of a trip is the “sweet spot” for fare savings”. READ:  Air France innovations help to take the stress out of travel. Booking flights on a weekend is a little less obvious. The analysis found average ticket prices tended to be lower when booked on a weekend, usually on a Sunday.  An exception was New Zealand, where the cheapest day is Tuesday. There was no explanation as to why this was but the outlook said many people save up to 20 percent by booking on a Sunday and some could save up to 36 percent. Thursdays and Fridays tended to be the expensive days for booking a flight but good days on which to depart on one. “Travelers can save around 10 percent on airfares simply by choosing flights that take off on a Thursday or Friday,’’ the report said. Extending weekday trips to include a Saturday night could also save money, according to the analysis, this time by about 25 percent. “For some popular corporate travel destinations where weekday travel is in high demand, the data show return airfare costs can be almost halved if travelers add a Saturday stay to a weekday trip,’’ it said. “The London-New York City route is one example.” Of course, extending a stay adds to accommodation costs but the study has advice there too: booking hotel stays on a Friday produces the lowest prices. And don’t book your hotel on the same day you book your airfare because Sunday is the most expensive day to book accommodation. Another tip urges travelers not to assume that direct flights are more expensive than those with stops.  This can be true but is not always the case, so it pays to check. Travelers are also advised to look at bundling accommodation and flights to save money and consider whether booking a no-frills ticket such as basic economy is, in fact, a false economy. It pays to add up all those costly extras and compare the total price for the travel. The study looked at ARC round-trip data between October 1, 2017, and September 30, 2018, as well at bookings at more than 895,000 properties offered by Expedia.