UPDATE: A source in Costa Rica tells E! that Britney Spears arrived with Mel Gibson at 3:18 p.m. local time.

Upon arrival, Britney looked calm, albeit tired, from the trip. Along with Gibson, his wife, Robin, and Britney's father, Jamie Spears, some unidentified youngsters also got off the plane.

An immigration executive boarded their jet to complete the necessary paperwork and, about an hour later, the group took off on a smaller private plane for the province of Guanacaste, in the northwest part of Costa Rica bordering Nicaragua.

Local press are reporting the pop star will be vacationing on Gibson's coastal property along Playa Barrigona.

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Britney Spears has found herself a rather unorthodox traveling companion. So to speak.

E! News has confirmed the singer joined Mel Gibson aboard a private jet this morning, bound for Costa Rica.

The unlikely, but not unprecedented, duo was joined on their trip by Spears' father, Jamie, and Gibson's wife, Robyn.

Though the exact nature of the trip is not yet known, it appears to be nothing more than a friendly weekend getaway, with a source telling E! News the group departed from Los Angeles with the intention of hanging out at Gibson's Costa Rica property "for a couple days."

The source also told E! News the showbiz pair's budding relationship has been nurtured of late by attorney Blair Berk, who repped Gibson in his infamous DUI arrest and who is currently representing Spears' parents in their various legal entanglements.

More recently, Gibson has been described as "mentoring" the troubled pop star and that the duo has discussed "a getaway" of some sort.

The surprising pair first raised eyebrows last March, when they, along with a group of mutual friends, were spotted dining together at Studio City eatery Romanov.

At the time, sources close to both stars denied any professional collaboration, insisting instead that their meeting was "all about sobriety" and that the Gibson clan was simply looking to help the young star.

Judging by her progress made in the past few months, it's a job well done.

—Reporting by Claudia Rosenbaum and Ken Baker

(Originally published May 15, 2008 at 11:05 a.m. PT.)