Details on the event from Disney:

Passholder In-Park Preview for Pandora – The World of AvatarYou’re invited to get an early peek of a groundbreaking destination–Pandora – The World of Avatar at Disney’s Animal Kingdom theme park. Here, you’ll be among the first to experience expeditions where you can fly on the back of a banshee, walk under floating mountains and navigate a mystical Na’vi River. You’ll also be able to purchase international-inspired cuisine from Satu’li Canteen and merchandise from Windtraders. This world beyond belief awaits you.Passholders can pre-register by making an online reservation for one in-park preview time slot. Event capacity is limited. Please note the number of reservations for this event is limited and subject to availability. There is no additional charge for this in-park preview with valid theme park admission.Please note: as this is an early exploration, access to specific activations and some areas of the Valley of Mo’ara within Pandora – The World of Avatar may be limited during your visit.All Guests must be Passholders in order to register for a time slot to preview Pandora – The World of Avatar.Guests may only register for one (1) time slot over the course of the preview period.If an Annual Passholder would like to register a Guest to accompany them, that Guest must also have a valid annual pass for admission to the event’s theme park location on the date of the event, be listed on your Family &Friends list and have opted to share “All My Plans” with you.Passholders with confirmed reservations will receive an additional email with details on how to check in for this experience, by May 12, 2017.All Guests must present their valid annual pass (or linked MagicBand), government issued ID and confirmation page to a Cast Member in order to enter Disney’s Animal Kingdom theme park and Pandora – The World of Avatar on the date of your preview.Availability is subject to change without notice.Event is subject to cancellation in the event of inclement weather.Guests must meet appropriate boarding and height requirements for the attractions.Capacity is limited and will be available on a first-come, first-served basis.Due to limited capacity, modifications to existing reservations will not be available.Limit one reservation per Passholder. Reservations are nontransferable and void if sold or otherwise transferred.

Registration is open now at this link it is filled on a first come first serve basis.