Brad Pitt and Angelina Jolie‘s secret relationship has reached new heights after they shared a secret ride in a private jet plane.

Hollywood’s hottest couple enjoyed a romantic sunset flight from Los Angeles to Mexico City for the premiere of their new movie Mr. and Mrs. Smith, The National Enquirer can reveal. Whether the sexy Tomb Raider star and hunky Brad actually joined the infamous “mile high club” is still up for debate.

But, according to sources at Toluca Airport, where the stars’ plane touched down, Angelina arrived “looking refreshed and relaxed” for the premiere on June 8.

The stars have tried to avoid being photographed together ever since they were spotted beachcombing in Kenya with Angelina’s son Maddox in April. At the time, we reported how guests at the remote resort in Mombasa hardly recognized the superstars as they appeared like husband and wife.

Just hours before Brad and Angelina arrived in Mexico City, they’d made only a fleeting red carpet appearance together at the Los Angeles premiere of their new film. We can reveal, however, that they made sure they were together for the secret three-and-a-half hour flight to Mexico last week.

“Angelina looked happy and refreshed as she stepped off the plane in Mexico,” an insider said. “Both stars acted as if there was nothing going on between them once they had landed but they clearly felt comfortable enough to travel together while nobody was watching.”

The stars’ plane touched down shortly after 5 p.m. and Brad was the first to emerge. Wearing a T-shirt and sporting a new, dyed-blond hairdo, Brad headed straight for a black SUV. Moments later, Angelina, wearing a black outfit with a plunging neckline, made her way to a separate SUV, which took her directly to the premiere.

The event was followed by an exclusive after-party at the Santa Fe Center, where guests said the stars couldn’t wait to be reunited for their return journey home.

A source revealed: “Brad and Angelina left early and by 10 p.m. they were back at the airport. They took another private jet to San Diego and then continued their night flight together back to Los Angeles.”

Both stars have been reluctant to answer direct questions about whether they’re dating. Recent comments, however, suggest the couple may be cautiously trying to clear the path for going public with their relationship.

On June 7, just hours before the couple traveled to Mexico, Brad, 41, defended Angelina against being branded a “homewrecker” during a chat with TV host Diane Sawyer on ABC’s Primetime Live.

When asked if he and his co-star were embarking on a romance, he replied: “There’s still a lot to, I guess, put in to place… Listen, I don’t know what the future is just yet.”

And, in a recent interview with W magazine, Angelina, 30, also suggested she was waiting for their relationship to be defined. She said: “People want answers about what’s happening… but I need to know what’s happening first.”