Moviegoers are having no problem identifying Unknown, as the Liam Neeson thriller led Saturday’s box office with $8.9 million and is estimated to win at least the Friday-to-Sunday weekend with $21.8 million. The four-day holiday weekend is another matter, but we’ll get to that a bit later. First, Unknown has solidified Neeson’s status as an action star, and the 58-year-old Irish actor is drawing a unique crowd. According to Warner Bros., 89 percent of the film’s audience was at least 25 years old, and an astounding 54 percent were over 50. Throw in the fact that many older moviegoers wait a few weeks before heading to the theater, plus the PG-13 film’s “B+” rating from CinemaScore participants, and Unknown could display some impressive long-distance stamina.

However, despite its current No. 1 position, Unknown may wind up losing the four-day holiday weekend to Disney’s Gnomeo & Juliet. The G-rated animated musical nearly doubled its Friday gross with $8.4 million on Saturday, and is estimated to finish the three-day weekend with $19.4 million — a scant 24-percent drop from last weekend. The family film is projected to lead today’s box office, and with kids out of school for Presidents’ Day, it should top Monday’s chart as well. Both Gnomeo and Unknown are on pace for a four-day tally of around $26 million — it could very well be a photo finish.

I Am Number Four, which many thought would be the four-day weekend’s winner, will probably have to settle for third place. The $50 million sci-fi adventure collected an estimated $19.5 million for the three-day weekend, and should finish the holiday frame with a little less than $23 million. The movie’s Friday-to-Saturday jump of 23 percent was the lowest among the top 10, and that’s never an encouraging sign. Unsurprisingly, the PG-13 film was mostly appealing to younger moviegoers, with 68 percent of the audience between the ages of 12 and 34. Its overall CinemaScore was a “B+,” but those under 25 handed Number Four an “A-” grade. Any hope for a sequel rests with those young fans spreading the word and returning to the theater — a lot.

The romantic comedy Just Go With It, starring Adam Sandler and Jennifer Aniston, slid only 40 percent (most Sandler movies fall around 50 percent) for a three-day estimate of $18.2 million. And Martin Lawrence’s third Big Momma movie, Big Mommas: Like Father, Like Son, consumed $17 million during the three-day frame. Add in a Presidents’ Day dessert, and the PG-13 comedy should finish the long weekend with just less than $20 million. Check back here on Monday for the complete box office report.

The following are three-day studio estimates:

1. Unknown — $21.8 mil

2. I Am Number Four — $19.5 mil

3. Gnomeo & Juliet — $19.4 mil

4. Just Go With It — $18.2 mil

5. Big Mommas: Like Father, Like Son — $17.0 mil