Tom Cruise so desperately wants the action caper “Knight and Day” to be his ticket back to the A-list. Enlisting the bubbly Cameron Diaz for this flirty, globetrotting adventure helps his cause, but the film can’t overcome the nagging feeling that we’ve seen it all before.

Call it “Mission: Impossible” for the Rom-Com crowd.

Cruise plays a rogue spy named Roy Miller. He’s protecting a pocket-sized power source that a few of his corrupt government cohorts want to sell on the black market. At a Kansas airport, he bumps into June (Diaz), a plucky mechanic on her way back to Boston for her sister’s wedding. Both board a nearly empty plane, flirt, drink and pretend to ignore the greasy-looking thugs doubling as fellow passengers.

When June retires to the lavatory, Roy takes down the rogue passengers, accidentally shoots the pilot, and now must explain the whole convoluted problem.

Director James Mangold (“Walk the Line,” “3:10 to Yuma”) nails the tone of these frenzied opening minutes. He uses June’s inexperience in combat as a way to speed the movie through the genre’s standard globetrotting time-sucks. Any time the situation gets hairy, Roy drugs June and drags her to where she needs to go, leaving the audience with only the occasional hazy glimpse of the mayhem.

Cruise and Diaz spark a lively chemistry, with Cruise seeming especially happy to play such dire consequences with a smile on his face. And it’s nice to see Diaz working in the same tough-girl-next-door wheelhouse that made her a star from “There’s Something About Mary.”

Sadly, “Knight and Day” stumbles the rest of the way. Even with the movie skimming over all the dull travel sequences, Mangold can’t establish a consistent pace. Cruise and Diaz banter less and less as the film chugs along, and the legion of henchman, led by a slumming Peter Sarsgaard, never establish any aura of danger.

The first act works because we get a lighter, breezier dose of Cruise’s inherent star wattage. But both stars fall into old traps as the movie goes along. Cruise’s default is “Frowning Mr. Impossible Mission,” and Diaz’s role unravels into the standard female tag-along.

Watching the story march to its predictable finish got me thinking: Why not reverse the roles? Have Diaz play the charming superspy, and stick Cruise in there as the awkward civilian who hyperventilates at the mere sight of a weapon. The switch would allow both actors to try different comedic beats, and the movie could coast better through its flimsy premise.

But a meek pencil-pusher taking orders from the “hair-gel” actress probably isn’t the role Cruise needs to get back into his beloved Action Movie Megastar circle. Instead we have “Knight and Day,” a movie we’ve already seen one time too many.

Grade: C+