The passion between Sienna Miller and Rhys Ifans burns so hotly that not even cramped quarters, a diminished oxygen supply and questionable cuisine can quell it. The London Daily Mirror says it got an unwelcome eyeful of the overly affectionate pair "snogging, tongues a go-go," in front of fellow passengers (including James McAvoy) during a post-Oscars flight home from Los Angeles on Monday. "Imagine a soundtrack of slurping and squelching," the paper ookily describes of their business-class bussing. "Next came an interlude of hairstroking, petting and nibbling, interspersed with whispering to each other and laughing hysterically." At one point, the gangly Ifans purportedly stripped off his wine-stained shirt and proceeded to snuggle up to Sienna in her reclined, oversized seat, where they kissed and nuzzled under a blanket. The pair, who were first linked last summer, finally came up for air when dinner was served.

Rihanna and Chris Brown at the 2007 VMAs

Rihanna and Chris Brown appear to be done treading water when it comes to rumors of a red-hot romance. Paparazzi caught the button-cute musical couple openly cuddling in a hotel pool during a sojourn in Jamaica a few days back. "They were smooching in the pool and were really lovey-dovey," an eyewitness tells PageSix.com. "They were playfully making out and he was kissing her on the neck." But the bikini-clad chanteuse apparently didn't want things to get too playful. "They were floating together with him carrying her and she kept saying, 'Don't get my hair wet,'" recalls the spy. "She was very soft and feminine but he was a big kid and splashing around." Their chlorinated snuggle-bunnies come just days after Chris, 18, serenaded RiRi at her 20th birthday celebration in Los Angeles. According to People, he may have also presented her with a $60,000 diamond and pink sapphire necklace and a $50,000 ruby and diamond heart pendant.

Has Jamie Lynn Spears' purported plan for a post-baby carriage marriage hit a speed bump? PageSix.com says despite a People report that Brit's expectant little sis, 16, is hoping to make things legal with beau Casey Aldridge, 18, during a ceremony this summer, her dad, Jamie, and mom, Lynne, are definitely not onboard. "Jamie thinks she is too young," says a snitch. "Her mom, Lynne, is stressed out about the whole thing."

In between hanging with BFF Katherine Heigl, T.R. Knight has apparently found time to meet someone new. People reports the "Grey's Anatomy" actor, 34, made the scene at Elton John's annual Oscar bash with a philanthropically minded and academically accomplished college student named Mark Cornelsen. The seemingly age-mismatched pair was snapped holding hands at the charity fete, although for now the actor's reps are mum on their status.

Next: Orlando's Short-Attention Span Affections?