ET breaks news that BRITNEY SPEARS and MEL GIBSON are currently en route to Costa Rica on vacation together! Britney arrived on time, about 5 minutes after Mel, and the plane departed at 9:05 a.m.

We spotted them leaving on a private plane to the Central American state early this morning. Sources tell us that Mel is taking Britney and her father JAMIE for a mini-vacation. We've learned they will be guests at Mel's home in Costa Rica.

According to the terms of her custody Britney's children cannot leave the country without special approval. There is no confirmation as to whether she sought approval and we're told they are not joining her on the trip.

While the pop star and the actor may appear to be an unlikely duo, they used to live in the same Malibu community and were spotted having dinner together at Studio City's Romanov restaurant in March.