Conor McGregor has left Ireland for the United States to face charges over his alleged attack on a bus filled with fellow mixed-martial arts fighters in April.

The 29-year-old and his associates were filmed "storming the building", smashing windows and throwing a chair and a metal guard rail at the bus parked at New York's Barclays Centre for the UFC 223 fight.

"The Notorious" will stand trial at Brooklyn Criminal Court at 9am local time (1am NZT) and could face seven years' jail if found guilty over the alleged wild attack.

McGregor posted an Instagram photo on Tuesday of himself with son Conor Jr and MMA fighter Cian Cowley, who was also charged over the incident, waiting to fly out of Dublin Airport on a corporate jet.


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He also shared a post of himself with Cowley that appeared to reference the trial with the caption, "from the cells to the stadiums. Not a scratch. They done nothing. Jet leaves Tuesday my brother."

Both men turned themselves in to police after the incident outside a UFC news conference on Thursday, April 5, before McGregor was released on $65,000 bail and Cowley on $30,000.

"He's the most visible face on the planet. He has no criminal history and the bail package is completely appropriate," McGregor's lawyer Jim Walden told the court.

Two athletes were injured by flying glass in the clash and McGregor was caught on CCTV repeatedly punching a security guard, the Brooklyn Court heard at his arraignment.

Lightweight Michael Chiesa was hospitalised and treated for cuts to his face and flyweight Raymond Borg was left with multiple corneal abrasions. Both their fights that Saturday were cancelled. "I'm devastated to say the least," tweeted Chiesa.

UFC vice-president of athlete development Reed Harris, who was on the bus, tweeted after the incident: "We thought we were gonna die."

Harris, who later deleted the post, added: "I've been in dozens of scuffles in UFC. Never once was I scared.

"This time was different."

Just 24 hours earlier, UFC president Dana White had said "it would be awesome if Conor McGregor was here", but he did not believe the Irishman had any plans to attend.

White said afterwards that McGregor had "loaded up the plane full of guys from Ireland" and co-ordinated an attack that was "the most disgusting thing that has ever happened in the history of the company".

Say what?😱😳 #Fight

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The meltdown reportedly came after McGregor heard of the UFC's decision to strip him of his lightweight title and award it to Khabib Nurmagomedov due to inactivity.

The Irishman tweeted that morning: "You's'll strip me of nothing you's do nothing c**ts."

The fighter reportedly decided to travel to New York to defend his friend Artem Lobov β€” who was also present for the incident β€” after he had clashed with Nurmagomedov in a hotel lobby in the city days earlier.

The Irishman has now been on an almost 19-month hiatus, but White revealed at the weekend that his next opponent will be lightweight champion Nurmagomedov.

McGregor faces a string of charges including three counts of misdemeanor assault, one count of felony criminal mischief, attempted assault, menacing and reckless endangerment.

Cowley, 25, was also charged with felony criminal mischief. "It was nothing," the younger man told Metro. "We'll just get it out of the way and then get back to work.

"Well, I have been working anyway. It was nothing, it was all blown up. That's not even in my head anyway."