Tom Cruise should go bonkers more often. At least on screen, that is.

As a rogue CIA agent in the zippy romantic thriller “Knight and Day,” the enigmatic actor plays to his strengths by showcasing his charisma, athleticism and — best of all — devilish twinkle in those killer baby blues.

Considering Cruise’s spotty recent track record — the barely decent “Valkyrie,” the hysterical “Tropic Thunder” and the preachy “Lions for Lambs” — the international Golden Boy must be itchin’ to slug one outta the park.

“Knight and Day” falls a bit short of that. The frothy confection is more of a line drive up the middle. Fortunately, “Knight’s” blunders arrive late and are negligible: A couple of scenes show the strains of working overtime in a film that, till then, is charmingly breezy.

Why director/co-writer James Mangold’s (“3:10 to Yuma” and “Walk the Line”) carefree homage to globe-trotting capers like Audrey Hepburn’s “Charade” works so effectively has more to do with teamwork than plot. Everyone realizes what the goal is: A light-hearted, action-packed thriller anchored by a cute romance, crazy stunts and clever one-liners. A tall order to execute, but obviously there are pros at work on “Knight and Day.”

The plot is pure malarkey. Perky June Havens (an adorable Cameron Diaz) unwittingly becomes tethered to renegade Roy Miller (Cruise) after bumping into him at the Wichita airport. The two cozy up while on a curiously empty flight that erupts into chaos (the funniest scene) once June visits the restroom.

When she returns, she discovers that the dreamy guy with the killer smile is lugging around a carry-on stuffed with issues. Not only is he being hunted by CIA members (“An Education’s” Peter Sarsgaard and “Doubt’s” Viola Davis) pursuing a mysterious device called “The Zephyr” (clever nod to Hitchcock’s MacGuffin plot device), but Roy appears to be cuckoo and trigger-happy. Before June knows it, she’s pulled into the vortex of his insane but exciting world.

This goofy setup opens the door for Mangold to stage tautly choreographed fights on planes, trains and automobiles (the most exciting takes place in the thick of Boston traffic) as the duo get chased here, there and everywhere. It also gives the versatile director carte blanche to take us on a nice vacation, with pretty stops in Spain, Austria and the tropics.

All of these elements make “Knight and Day” grand mindless fun. Yet its greatest success hinges on the chemistry between the leads. Cruise and Diaz make an impossibly gorgeous pair and have a potent on-screen connection. When they swoon, we want to swoon and sigh right along with them. (And by the way, Diaz wins the title of the Best Baby Blues).

After so many bad romance movies, it’s a treat to see genuine sparks fly between two major stars. That the budding relationship evolves over the course of bullets, die-hard assassins and chiseled torsos increases the pleasure.REVIEW