The film's investors offset funding costs by paying Cruise a lower advance fee and providing him a share of revenue only after the financiers were repaid their investment in the production. Filming took place in several locations, mainly in several cities located in Massachusetts, while other scenes were filmed in Spain and parts of Austria.
The film was officially remade in Bollywood with Hrithik Roshan and Katrina Kaif in the lead roles titled Bang Bang! and released on 2 October 2014.
After colliding with Roy Miller (Tom Cruise) twice in the airport departure terminal on the way home from Wichita to pick up car parts, June Havens (Cameron Diaz) is told she has been bumped to a later flight. C.I.A. Agent John Fitzgerald (Peter Sarsgaard), believing Havens is working with Miller, puts her back on the plane. Completely taken with Miller, Havens goes to the restroom to prep herself up. Meanwhile, Miller fights and kills everyone else on the plane, even the pilots, who were all agents sent by Fitzgerald. After Havens reemerges and gives him a kiss, Miller crash-lands the plane in a cornfield. He drugs a shocked and confused Havens, warning her about the agents who will come after her and that she is not safe with them.
Waking up at home, Havens struggles through a day fitting a bridesmaid's dress for her sister's wedding, and is shocked to learn her sister would like to sell their father's 1966 Pontiac GTO tri-power, which Havens had planned on finishing as a wedding present. Havens is then picked up by a group of intelligence agents, led by Fitzgerald. Miller arrives and, through a long gunfight on the highway, kills several agents and reclaims Havens. She flees at the first opportunity and contacts Rodney (Marc Blucas), a firefighter and former boyfriend. Believing Havens is merely stressed and is playing out a fantasy, Rodney takes her out and she tells him everything that has happened to her, though he still does not understand. Miller then arrives and pretends to take Havens hostage while holding everyone else at gunpoint, fleeing with her.
Miller explains that Havens is safer with him and she agrees to follow him as they go to pick up Simon Feck (Paul Dano), a genius inventor who has created a perpetual energy battery called the Zephyr. Traveling to Brooklyn, Miller and Havens discover that Feck has fled from the warehouse he was hiding in, leaving a clue for Miller about his location. They are then attacked by henchmen sent by Spanish arms dealer, Antonio Quintana (Jordi Mollà). After again being drugged, Havens drifts in and out of consciousness between their capture and escape from Quintana's men, and Miller brings her to an island that is off-the-grid, which Miller uses as a safe house. Accepting a call from her sister after leaving in frustration, Havens accidentally leads Quintana's men straight to the hideaway. They try to kill Miller and Havens with an unmanned aerial vehicle. Before they escape by helicopter, Havens is knocked-out by Miller since she is afraid of flying.
Miller reunites with Feck and they, with Havens, get on a train heading for Austria. Havens is attacked by Bernard (Falk Hentschel), an assassin sent by Quintana to retrieve the Zephyr and Feck, and kill Miller. But Miller and Havens fight him and he is killed by another train. Arriving at Salzburg, the three check into a hotel. Miller later leaves to meet with Naomi (Gal Gadot), Quintana's henchwoman, to make a deal. Havens follows him and listens to Miller's conversation, mistaking that he does not care for her. She is then picked up by Fitzgerald and C.I.A. Director Isabel George (Viola Davis), who reveal that Miller was using her at the airport to smuggle in the Zephyr when they bumped into each other and convince her that he doesn't love her. They also tell her that Miller is the traitor and plans to trade the battery with Quintana. Heartbroken, Havens allows the C.I.A. to find Miller back at the hotel. Miller escapes with the battery, but is seemingly shot on the rooftop and falls to his death in the river. Feck is taken into custody afterwards to Schwedelbach, Germany, though it is later revealed that Fitzgerald has been the real traitor all along and he captures Feck.
Returning home, Havens heads to an address she remembered from Miller's iPhone, where she finds his parents and learns that his real name is Matthew Knight. They believe their son, a former Army sergeant and Eagle Scout, is dead; but they are fabulously wealthy from winning lotteries and sweepstakes they don't remember entering. Leaving a message on her own answering machine that she has the Zephyr, she is captured by Quintana's men and taken to Sevilla, Spain. She is drugged with truth serum before being rescued by Miller, who was tracking Fitzgerald, who was delivering Feck to Quintana.
Chaos erupts throughout the streets and Quintana is killed by a bull stampede. At the docks, Miller saves Feck from a bullet wound after handing over the Zephyr in a small pouch. Feck later reveals that the battery is unstable and it explodes, killing Fitzgerald. Miller collapses from the gunshot and is hospitalized in Washington D.C.. George apologizes to Miller about him and Fitzgerald, but tells him to let go of Havens and return to the C.I.A. Miller is later drugged by a nurse, who turns out to be Havens. After Havens breaks Miller out of the hospital, he wakes up in the rebuilt GTO that belonged to her father. After Miller asks what day it is, Havens kisses him and says it is someday. This is a reference from the start of the film that they both have things they want to do someday, and Havens begins to drive towards Cape Horn. As the credits begin to roll, Miller's parents unwittingly receive tickets to Cape Horn in the mail and accept to go.
Before film director James Mangold signed on to Knight and Day, it was previously associated with director Tom Dey. More than 12 writers contributed to the film, and the Writers Guild of America, West decided due to this large number of contributors, to only credit Patrick O'Neill – who had put in effort on the beginning layout of the script. Other writers that worked on the film's script included Scott Frank, Laeta Kalogridis, Ted Griffin, Dana Fox, and Simon Kinberg.
The film changed lead cast members multiple times while the production was mired in "development hell". Prior to the finalization of actors Tom Cruise and Cameron Diaz, comedian and actor Adam Sandler was offered to star in the film when it was titled Wichita, but declined explaining, "I just don't see me with a gun." Wichita was developed under production at Revolution Studios; the film was later moved to Sony Pictures. At Sony Pictures, actors Chris Tucker and Eva Mendes were slated to portray the two lead roles in the film; it was titled Trouble Man and intended as a romantic vehicle film for Tucker and Mendes.
After Tucker and Mendes dropped out of the lead roles, Diaz signed on to the film with Sony Pictures, and actor Gerard Butler met with production staff regarding starring opposite Diaz. Butler instead decided to take on the lead role in the film The Bounty Hunter, opposite actress Jennifer Aniston. Tom Cruise considered accepting a role in the film; at the time he was auditioning for parts in five films including Salt, and The Tourist. Cruise decided he wished to star in Knight and Day, and had a vision for the film which included modifying the male lead character with his own ideas. Other actors cast in the film included Maggie Grace, Peter Sarsgaard, Marc Blucas, Paul Dano, Viola Davis, and Jordi Mollà.
The film's production partners, New Regency and Dune Entertainment, offset financing for the film by paying Tom Cruise a lower advance fee than he normally received. Cruise previously garnered $20 million or higher in an advance fee, but the Los Angeles Times reported he only received $11 million for Knight and Day. Cruise will also not receive "first dollar gross", which was customary for him. This means that Cruise will not receive a share of the film's revenue, until Knight and Day funding investors have first gained back their investment in the production. In total, production costs for the film exceeded $125 million.
Principal photography began in mid-September 2009 in Boston and Bridgewater, Massachusetts. Airport terminal scenes were filmed at Worcester Regional Airport. Filming also took place in Melrose, Danvers, and New Bedford, Massachusetts. Spanish cities Seville and Cadiz, as well as Austrian city Salzburg, were also chosen as locations.
The Black Eyed Peas recorded a theme song for the film, titled "Someday".
Knight and Day had been set for a June 25, 2010, release date, but FOX moved its debut up two days to June 23; in the face of poor initial tracking numbers. The New York Observer analyzed the marketing for the film, which included an attempt at pushing a "viral video" of the two main stars; journalist Christopher Rosen commented on the desperation level of the publicity campaign, "the marketing for this thing has seemed more intrusive and desperate than any other big-ticket release in some time." Film producer Don Carmody commented negatively regarding the film's trailer, calling it "dull", and stated the film would not do well because of the age of its two stars, "Cameron Diaz I think was a star, but she’s no longer a star. Some of those stars are getting a little up there (in age)." The Hollywood Reporter noted, "potential viewers remain startlingly indifferent to whether they actually end up seeing it. And attention thus far is still drawn mostly by those under 25, which indicates that the fans who grew up with star Tom Cruise have moved on."
FOX attempted to increase word of mouth advertising for the film by showing a sneak preview on June 19, 2010; the Los Angeles Times reported the same day that pre-release surveys determined that the film was likely to become a commercial flop. Projections indicated that the film would only make $20 million at the box office; the film cost $125 million to produce. FOX production President Emma Watts commented of the film's commercial prospects, "We aren't exactly where we hoped we would be." Los Angeles Times noted, "In addition, Cruise and Diaz are not as popular with younger moviegoers, who often drive big opening weekends in the summer. ... Among teenage and college-age males, the movie is barely registering, according to people who have seen the survey results." New York Magazine reported the film was "tracking miserably" prior to its first week. New York Magazine reported that an issue with Knight and Day was, "one of the film's biggest handicaps: its star, Tom Cruise". A FOX official commented to New York Magazine regarding the film's pre-release polling data, "at those numbers, we can’t open the movie right now. Hopefully, they’ll change in the next few days."
Upon hearing that tracking data on June 22, 2010, showed the film was not likely to produce revenue over $30 million in its first five days on screen, a FOX executive told TheWrap he was "confounded", and commented, "Tracking says one thing, but our sneak previews this weekend said something totally different. ... but if you look at the empirical data, we’re nowhere." New York Magazine reported that the day prior to the film's release, a long scene from Knight and Day was made available on iTunes, in an attempt to improve the lackluster 28–31% "definite interest" level of the movie. After results were reported from the film's initial debut, FOX distribution executive Bruce Synder commented to The Hollywood Reporter, "It's an adult movie opening on a Wednesday, but we opened it there and snuck it on Saturday because we believe the word-of-mouth will be good, so we're set for a pretty good opening weekend. Remember, it's an original, adult movie, which we expect will run for quite a while."
An 'extended cut' which added eight minutes of footage, mostly extended versions of existing scenes, as well as a new opening scene that better established June Haven's profession as a mechanic was released on Video On Demand in North America. As of January 2011 it had not been released in DVD region 1, though it had been released in regions 2, 3, and 4.
Knight and Day performed poorly at the box office in its debut, with a take of US$3.8 million the day after its initial June 23, 2010 release in revenue from ticket sales in the United States and Canada. This was less than the film Toy Story 3, which earned $13 million at the box office on the same day. Knight and Day did not place within the top 50 all-time Wednesday film openings. An analysis of the opening day results by Box Office Mojo noted it was the worst attended action film debut for Tom Cruise since his appearance in the 1986 Legend. It was the lowest-grossing opening day for Cruise in a leading role since his performance in the 1992 film Far and Away. Cruise's last starring role prior to Knight and Day, in the 2008 film Valkyrie, generated $8.5 million on its opening day. The previous film with Cameron Diaz and Cruise as the lead roles, Vanilla Sky, garnered $8.9 million on its opening day. Moira Macdonald of The Seattle Times characterized the film's initial revenue results as "a box-office disappointment"; Lou Lumenick of New York Post commented, "Not great numbers"; journalist Roger Friedman noted for Hollywood News, "Bad reviews didn’t help. 'K&D' has registered only 52% on Rotten Tomatoes. Even those reviews counted as positive weren’t so good. They were stretching."; Nicole Sperling of Entertainment Weekly noted, "audiences just aren’t showing up the way Fox might have hoped"; and Ben Fritz of Los Angeles Times called the film's debut a "soft" opening, and commented, "It wasn't a good first day or night at the box office for 'Knight and Day.'"
The film's revenues dropped nine percent on its second day of release, earning $3.5 million in ticket sales. During the same period that revenues dropped for Knight and Day, ticket sales for Toy Story only fell by three percent, The Karate Kid dropped by six percent; while other films increased revenues at the same time, including, Shrek Forever After, Sex and the City 2, Get Him to the Greek, Killers, and Robin Hood. In its first weekend, Knight and Day was paired up against Grown Ups, a comedy film starring Adam Sandler, Kevin James, Chris Rock, David Spade and Rob Schneider. The Friday of its first weekend after release, Knight and Day took third place at the box office, behind both Grown Ups and Toy Story 3. The film brought in a total of $6.4 million on its third day of release.
Knight and Day received mixed reviews from critics. On Rotten Tomatoes the film has an approval rating of 52% based 221 reviews with an average rating of 5.6/10. The site's critical consensus reads, "It's pure formula, but thanks to its breezy pace and a pair of charming performances from Tom Cruise and Cameron Diaz, Knight and Day offers some agreeably middle-of-the-road summer action." On Metacritic, the film has a score of 46 out of 100 based on 38 critics, indicating "mixed or average reviews". Audiences polled by CinemaScore gave the film an average grade of "B+" on an A+ to F scale.
The film received a negative review in Variety; critic Justin Chang characterized the film as "a high-energy, low-impact caper-comedy that labors to bring a measure of wit, romance and glamour to an overworked spy-thriller template". Kirk Honeycutt of The Hollywood Reporter summarized his review of the film with, "Bottom Line: Logic and plausibility take a holiday in this nonstop actioner that counts on stars Tom Cruise and Cameron Diaz to sell the nonsense." Honeycutt wrote of the writing, "the script is too lazy to develop any of its characters – and that includes the leads", and commented, "laziness permeates the film from the inexplicable escapes to the neglected romance". Knight and Day received a rating of one and a half stars from a review by Michael Phillips in the Chicago Tribune; which criticized multiple aspects of the film, including its script, directing, cinematography, set pieces, and action sequences. Phillips concluded, "A 21st Century 'Charade' pumped up on all the wrong steroids, 'Knight and Day' may well suffice for audiences desperate for the bankable paradox known as the predictable surprise, and willing to overlook a galumphing mediocrity in order to concentrate on matters of dentistry." Lexi Feinberg of Big Picture Big Sound gave the film a rating of one and a half stars, and characterized it as an "asinine, action-adventure dud", with a "stupid plot". Feinberg commented, "'Knight and Day' is a ludicrous, large-scale failure".
In a review of the film for the New York Post, critic Lou Lumenick rated Knight and Day with one and a half out of four stars. Lumenick wrote, "this is a big, dumb summer movie with no apparent ambition other than plugging a hole in a studio’s schedule because its faded star happened to be available for a few weeks." American film critic and professor Emanuel Levy was critical of the film's writing, calling it a "mindless flick"; he noted, "The story moves at a breakneck speed, as if to conceal the incongruities in the storytelling." Levy gave the film a grade of "C", and commented, "Preposterously plotted, the saga is dominated by long, energetic, uneven action sequences, but it lacks any logic and pays minimal attention to characterization. Repetitious in structure, and with humor that more often than not misses the mark, 'Knight and Day' is characterized by nihilistic violence and amoral tone, which wouldn't have mattered had the movie been witty or fun to watch." Simon Abrams of Slant Magazine gave the film a rating of two stars out of four, and commented of the film's director and writer, "Clearly O'Neill and Mangold are trying to give viewers what producers would undoubtedly like to sell as 'something for everybody,' but there's no consistency to the thing and no chemistry whatsoever between Cruise and Diaz, making the alternating tug-of-war between girly and manly elements of the film seem extraordinarily forced." In a review published in The Victoria Advocate, Robert Philpot of McClatchy Newspapers called the movie "disposable", and singled out the film's script as its "biggest problem", commenting that it "feels lazy right from its lame-pun title". The Miami Herald film critic Rene Rodriguez wrote that there was "no chemistry between Cruise and Diaz", and commented regarding Cruise's acting, "Tom Cruise spends much of 'Knight and Day' looking as if he's waiting for someone to pour casting mold over his head to make an action figure."
Entertainment Weekly film critic Lisa Schwarzbaum gave Knight and Day a grade of "C+", and compared it to the 2010 film Killers starring Katherine Heigl and Ashton Kutcher, "The producers assume that audience interest in movie stars is bigger than audience interest in characters. The conclusion is overdetermined, since Roy and June are such flimsy constructions. ... At least they're not Katherine Heigl and Ashton Kutcher in Killers." Colin Covert of Star Tribune made a similar comparison, "The film looks unambitious, like a remake of 'Killers,' the Ashton Kutcher-Katherine Heigl guns-and-giggles toss-off everyone has already forgotten, but with bigger stunts and more star wattage." The film received a rating of two stars out of four from critic Peter Howell in the Toronto Star; the reviewer commented, "There is supposed to be romance in Knight and Day — and Diaz is up for it — but Cruise still looks as if he’s taken charisma lessons from Al Gore." In a review for The Huffington Post, critic Marshall Fine observed, "the movie bubbles happily for almost an hour before it flags". Robert Bell of Exclaim! wrote of the script, "Sure, things slow down a bit around the midway point, making it clear that there is very little going on here aside from cheesy escapist fantasy, but things quickly pick up again, engaging us in the moment of a movie that knows exactly what mainstream trash cinema should be." In a review for the Orlando Sentinel, critic Roger Moore commented, "The blase plot devices (a gadget, the nerdy guy who invented it), the bland villains, the too-fast dash through exotic locales, don't matter so long as Cruise and Diaz click and spark their scenes – chases and embraces – to life. And Cruise, hurling himself at this as if his Mission: Impossible future and indeed his whole career depended on it, makes sure they do."
The Wall Street Journal critic Joe Morgenstern commented, "'Knight and Day' woke me up to just how awful some summer entertainments have become. It isn't that the film is harmful, except to moviegoers' wallets and movie lovers' morale, but that it is truly phenomenal for the purity of its incoherence." Writing for the Chicago Sun-Times, Roger Ebert rated the movie 3 stars out of 4 and wrote, "'Knight and Day' aspires to the light charm of a romantic action comedy like 'Charade' or 'Romancing the Stone,' but would come closer if it dialed down the relentless action. The romance part goes without saying after a Meet Cute contrived in an airport, and the comedy seems to generate naturally between Tom Cruise and Cameron Diaz. But why do so many summer movies find it obligatory to inflict us with CGI overkill? I'd sorta rather see Diaz and Cruise in action scenes on a human scale, rather than have it rubbed in that for long stretches, they're essentially replaced by animation." Ty Burr of The Boston Globe stated, "The movie’s a piece of high-octane summer piffle: stylish, funny, brainless without being too obnoxious about it, and Cruise is its manic animating principle." Writing for the Associated Press, Christy Lemire commented, "Cruise's presence also helps keep things light, breezy and watchable when the action – and the story itself – spin ridiculously out of control." Bill Goodykoontz of The Arizona Republic observed, "Mangold, working from a script by Patrick O'Neill, accelerates events in a way that is either a perfect representation of how current action films are made or a demonstration of everything that's wrong with movies today. Maybe it's both." Joshua Starnes of ComingSoon.net gave the film a rating of 6.5 out of 10, and concluded his review, "Instead of watching it, you're better off putting "Knight and Day" in a time capsule and singing some Don McLean, 'cause this is the day the movie star died." In a subsequent "mini review", Edward Douglas of ComingSoon.net gave the film a rating of 8 out of 10, and concluded, "The entertainment comes from how much fun it is watching [Cruise and Diaz] on screen together and that's what separates Knight and Day from previous attempts at mixing romance, comedy, and action." In a review for CNN, Tom Charity commented, "there's a creeping anxiety about this project, a tendency to over-compensate that speaks to underlying inadequacies."