How much does it cost for a plane not to land?

On June 22, a Brussels Airlines flight from Brussels to Washington, DC, turned around mid-air and went back to its starting point, meaning that passengers spent a total of nine hours in the air to essentially go nowhere.

According to Belgian website Aviation24, flight SN515 was beset with challenges from the beginning.

Originally, the flight was supposed to depart at 10:15 a.m. local time from Brussels. But due to a last-minute change of aircraft, it left two hours late.

That wasn’t all. The change in aircraft meant that the plane didn’t have the proper authorization paperwork for landing in the United States. Rather than risk a fine upon arrival at Washington-Dulles, someone made the decision to reverse course, and the plane made a U-turn somewhere around Ireland.

The plane landed back in Brussels at 9:15 p.m., clocking about nine hours in the sky. The airline cited “operational reasons” for the flight’s mid-air turnaround.

While turning a plane around mid-air is frustrating for passengers who were en route to their vacation or elsewhere, it’s also a massive headache for the airline who makes the call, especially for one based in Europe.

The European Union’s strict laws on passenger rights around flight delays mean that Brussels Airlines will have to pay up for its paperwork error.

The airline, which is part of the Star Alliance network, must pay each passenger €600 ($683) for the inconvenience, as well as put them up in hotels for the night and give meal vouchers.

But that’s not all. As the One Mile At A Time blog notes, Brussels Airlines will have to add in the cost of rebooking everyone and juggling around the crew so they don’t go over their maximum time allowances, meaning they could be looking at somewhere in the ballpark of €500,000 ($569,000).

“This is a costly move on Brussels Airlines’ part,” Scott Keyes, founder of the Scott’s Cheap Flights website and newsletter, tells CNN Travel. He also notes that Brussels Airlines has one of the worst on-time rankings in Europe.

Keyes advises that travelers who find themselves in a situation like this do as much as they can to know their rights.

In the United States, passengers on delayed or canceled flights do not have laws as strict as the one in the EU to protect them.

“The first thing that you should know, and that I always do when there’s a big delay or cancellation, I Google the travel protections on the credit card I used to buy the flight,” Keyes says.

He also advises keeping “a paper trail,” namely receipts for anything you purchase — whether it’s a meal in the airport or essentials you need to function until your delayed baggage arrives — as a record when you seek compensation from the airline and/or your credit card company.

While the Brussels Airlines “flight to nowhere” experience was undoubtedly frustrating, it is sadly not uncommon.

In 2017, model Chrissy Teigen spent eight hours on a similar flight — she was traveling from Los Angeles to Tokyo when the plane turned back around.

In that case, the reason for the reversal was “an unauthorized passenger” on the plane.

CNN has reached out to Brussels Airlines for comment.

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