Before you book your flights, you may want to think about changing the day you fly.

New research has found that flying on a Sunday is the worst day of the week.

The study, conducted by HappyOrNot, analyzed more than 4.5 million customer feedback points which are found across airports in 30 countries.

The data found that the worst day of the week was Sunday, as people were the least happy.

The report found that just 81 percent of customer feedback was positive.

The best day to fly? A Wednesday, where happiness was the highest at 84.6 percent.

Miika Mäkitalo, CEO of HappyOrNot, commented: “With an expected boom in summer holiday travel, we wanted to examine the experience of traveling through the airport – which can vary from being a smooth, enjoyable start to the holiday to being a frazzled, unpleasant few hours.

“By releasing these findings, we hope to equip travelers with the knowledge of when might be best to fly and the times they should probably avoid, as well as equipping airport operators with passenger experience data insights to be aware of as airports get busy again.” 

The research even found what time of day to fly, with midnight flyers being the least happy at just 77.3 percent positive feedback.

The happiest time was at 8 a.m., with 86.6 percent.

So if you want to be the happiest when traveling, it is best to book the first flight of the day in the middle of the week.

Forget the last flight on a Sunday as you will be the most miserable.

Flight attendants have also revealed why you should fly earlier rather than later, as it also means your flight is less likely to be delayed.

Former pilot Kathleen Bangs told Forbes: “The early bird gets airborne, statistically, with less delays and fewer cancellations.

“The later it gets in the day, the more likely your flight is to be delayed or canceled.

Frequent flyer Dan Birchall also said that in case of overbooking on the flight, an earlier flight gives you the upper hand with the airline.

A flight attendant also said that flying earlier will mean not only nicer crew, but much cleaner planes.

Nervous traveler? Choose an early flight too as a later flight means the ground has had more time to heat up, which can cause “bumpier air” and lead to turbulence onboard.

This story originally appeared on The Sun and has been reproduced here with permission.