LOS ANGELES (AP) — Liam Neeson has proven himself a known quantity again at the box office.

Neeson’s thriller, Unknown, debuted as the No 1 movie with $21.8 million, following in the footsteps of his 2009 action hit Taken, according to studio estimates.

Another action tale, I Am Number Four, opened at No 2 with $19.5 million.

A Warner Bros. release, Unknown stars Neeson as a botanist who awakens from a coma to find his wife claims she does not know him a nd that another man has taken his identity.

DreamWorks’ I Am Number Four stars Alex Pettyfer as a teenage alien refugee on Earth who develops superpowers to battle the evil invaders that destroyed his planet. It was the first DreamWorks movie released under the company’s distribution deal with Disney.

While I Am Number Four held youth appeal, Unknown was a rare No 1 film that did most of its business among older crowds. According to Warner, 54 per cent of the movie’s audience was 50 and over and 89 per cent was 25 and over.

The 58-year-old Neeson has had action roles before but found unexpected success as an all-out action hero with Taken, a $100 million hit.

“He’s the new man. He’s stepped up to the plate. Put him in the right role and he’s every man’s action star,” said Dan Fellman, head of distribution at Warner.

Two movies that opened the previous weekend held the next two spots in the top 10.

Disney’s Gnomeo & Juliet, was No 3 with $19.4 million, finishing so closely to I Am Number Four that the two movies could change rankings when studios release final numbers tomorrow, after the long President’s Day weekend. Gnomeo & Juliet raised its total to $50.4 million.

Adam Sandler and Jennifer Aniston’s romance Just Go With It, which had been No 1 the previous weekend, fell to fourth place with $18.2 million. The Sony release lifted its total to $60.8 million.

The weekend’s other new wide release, Martin Lawrence’s comedy, Big Mommas: Like Father, Like Son, was No 5 with $17 million. The 20th Century Fox sequel has Lawrence reprising his role as a federal agent who goes undercover as a hefty woman to crack a case.

Hollywood finally broke a long downturn in business during which revenues were off 14 straight weekends compared to last year’s.

This weekend, receipts totaled $144 million, up 7.7 per cent compared to the same period last year, according to box-office tracker Hollywood.com.

But compared to President’s Day weekend in 2010, which fell a week earlier, revenues this time were down 30 percent.

“Certainly not a record President’s Day weekend by any stretch, but it was a good weekend,” said Hollywood.com analyst Paul Dergarabedian. “It was solid but not spectacular, but at least it broke the down streak.”

Two top contenders at next Sunday’s Academy Awards hit the $100 million mark.

The Weinstein Co drama The King’s Speech, the best-picture front-runner, pulled in $6.6 million to lift its total to $103.3 million. Fox Searchlight’s psychosexual thriller, Black Swan, took in $1.3 million and raised its haul to $101.5 million.

Colin Firth of The King’s Speech and Natalie Portman of Black Swan are considered the favorites for the lead-acting Oscar awards.

1. Unknown, $21.8 million.

2. I Am Number Four, $19.5 million.

3. Gnomeo & Juliet, $19.4 million.

4. Just Go With It, $18.2 million.

5. Big Mommas: Like Father, Like Son, $17 million.

6. Justin Bieber: Never Say Never, $13.6 million.

7. The King’s Speech, $6.6 million.

8. The Roommate, $4.1 million.

9. The Eagle, $3.6 million.

10. No Strings Attached, $3.1 million.