UPDATE: According to final box-office numbers released by Box Office, an unexpectedly strong Sunday showing by The Hangover boosted the comedy to the top spot for the weekend box office with $44.98 million over $44.14 million for Disney/Pixar’s Up, which had held the No. 1 position in early b.o. estimates.

ORIGINAL TEXT (from 6/7/09): Buoyed no doubt by repeat business and premium 3-D ticket prices, Disney/Pixar’s Up lifted past the bona fide surprise hit The Hangover to be the first film of the summer to hold at No. 1 for two straight weeks at the box office. Well, maybe. Early estimates from Box Office have Up grossing an estimated $44.2 million to The Hangover‘s $43.3 million, a less than $1 mil difference that gives the R-rated comedy a chance to push to the top spot once actual figures are released tomorrow. Regardless of the final numbers, Up‘s estimated total gross of $137 million places it firmly in the upper echelon of Pixar earners.

Even if The Hangover doesn’t pop enough of Up‘s balloons to become No. 1, stars Bradley Cooper, Ed Helms, and Zach Galifianakis as well as director Todd Phillips (Old School) have a lot to celebrate. Not only did the film pull in an outstanding “A” CinemaScore rating, the craziest-bachelor-party-ever dude-fest managed to draw in just about as many women as it did men. That bodes well for the film’s staying power through the rest of the month, where its stiffest comedy competition will be the high-concept, ancient times Jack Black/Michael Cera flick Year One in two weeks.

And if Land of the Lost‘s box office fate is anything to go by, Black and Cera should be concerned. Will Ferrell’s high-concept comedy under-performed, grossing just $19.5 million for third place — nowhere near the star’s best opening weekends. Worse yet, the film earned a dismal C+ CinemaScore average; audiences ages 35 to 49, ostensibly the age group that would best remember the original 1970s kids TV series on which the film is based, gave it a D+. Ouch.

My Life in Ruins, star Nia Vardalos’ return to movies after a five-year absence, opened to just $3.2 million on 1,100 screens — which, actually, is slightly better than My Big Fat Greek Wedding‘s first weekend in wide release, but it’s probably best not to expect Greek lightning to strike twice. By contrast, the indie road dramedy Away We Go weathered mixed reviews to bank an estimated $143,000 on just four screens, for an outstanding $36,000 per-screen average.

Meanwhile, Night at the Museum: Battle of the Smithsonian took fourth place with $14.6 million, a solid 40 percent drop for a $127.3 million three-week total. Star Trek continued its fantastic run, dropping just 33 percent with $8.4 million for fifth place and $222 million overall. Sam Raimi’s horror-fest disappointed again, dropping 54 percent in its second week for a 7th place finish of $7.3 million (its cumulative total is $28.5 million). And Angels & Demons — which slipped to 8th with $6.5 million in U.S. box office for a $116 million stateside total — broke past $400 million in global earnings, making it the highest grossing film worldwide for 2009.

More from EW:

‘The Hangover’ hits a $16.5 mil jackpot on Friday

‘Drag Me to Hell’: Why didn’t it do better?