I don't think any federal charges have been filed, at least not yet.

He's still in custody, they did not yet raise the $2,500 needed to get him out and is on his way to Rikers now.

His court appointed lawyer says

At the arraignment on felony charges of reckless endangerment and criminal mischief in a packed room in the basement of criminal court, Mr. Slater’s court-appointed lawyer, Howard Turman, said that Mr. Slater’s activation of the slide was not reckless. He said Mr. Slater followed the proper procedure for activating the slide, checking out the window first to make sure no one was on the tarmac who could be struck by it.

Ok, that makes perfect sense, it's OK because he looked first.

The problem with this case, is there is probably nothing at all to really charge him with, they had to come up with those just to arrest him.