Plot

In the countryside of Yorkshire, the Tweedys, a middle-aged couple, run their chicken farm in Yorkshire, England. Mrs. Tweedy (Miranda Richardson) serves as the brains and temper, while Mr. Tweedy (Tony Haygarth) is rather slow but handles the manual work. The coop is run in the style of a World War II POW camp, with the chickens accountable for the number of eggs they lay daily. They kill and eat any chicken that is no longer able to lay eggs. The coop is like a prison with fences on all sides and locked gates. The dogs patrol the coop constantly.

One chicken, Ginger (Julia Sawalha), has attempted numerous plans to flee the coop, aided by contraband smuggled into the coop by two rats, Nick (Timothy Spall) and Fetcher (Phil Daniels), but is always caught by Mr. Tweedy and his dogs, and is thrown into the solitary confinement numerous times. Ginger's plans include digging under the fence, or even digging a whole tunnel from the coop to the outside jungle, or even using a combination of chickens to create a human shaped object dressed like a human.

Mr Tweedy suspects the chickens are organized and plotting resistance, but his wife dismisses his theories while being frustrated with making minuscule profits.

The other chicken on the farm include Babs (Jane Horrocks) a chubby chicken who loves knitting, Bunty (Imelda Staunton) the champion egg-layer and Mac (Lynn Ferguson) Ginger's Scottish second in command.

Meanwhile, Mrs. Tweedy realizes that her farm is failing and reads a catalog on an ambiguous method of increasing profits at her farm. Ginger, realizing something is wrong, attempts to convince the other hens to speed up their efforts to escape. However, she soon comes to the conclusion that the only escape route is to go over the fence, something chickens cannot do. Later the same night, as a depressed Ginger sits outside, a Rhode Island Red rooster named Rocky (Mel Gibson) seemingly flies over the fence and accidentally crashes into the coop.

The hens fawn over the new arrival, who introduces himself as Rocky. The chickens put his sprained wing in a cast and hide him from the Tweedys, who have been promised a handsome reward by Rocky's owner for his return.

Ginger is initially suspicious, til she finds the first half of a poster with Rocky on it. Showing it to the other hens and explaining how he came in, she claims that he can fly and attempts to convince Rocky to help her and the other hens escape by teaching them how to fly. However, Rocky's wing was injured, and he cannot show them immediately. Instead, Rocky puts them through a set of exercises that seem to have no purpose while assuring them that all the chickens are making progress.

Meanwhile, a large machine arrives, and Mr. Tweedy begins assembling it. The crate contained the parts for a chicken pie machine that Mrs Tweedy has ordered as part of a plan to convert the farm into a profitable pie-making factory.

At the same time, Tweedys increase the chickens' food rations and ignore the decline in egg production. Ginger unwisely proclaims that her intent is to fatten them up for something, causing a panic. After Ginger and Rocky get into an argument, Rocky holds a morale-boosting dance party during which it is revealed that his wing is healed. Ginger talks Rocky into agreeing to give a flying demonstration the next day.

However, the machine is now complete, and Mr. Tweedy kidnaps Ginger for its first test. Rocky follows Ginger into the machine and rescues her, sabotaging the machine and giving them more time to work on their escape. Fowler (Benjamin Whitrow), an older rooster, gives Rocky his respect for rescuing Ginger and his old Royal Air Force (RAF) badge in tribute. Rocky decides to flee the farm the next day, leaving behind Fowler's medal and the second half of the poster, showing that he was a stunt rooster, only "flying" by being shot out of a cannon.

This revelation outrages the other chickens, and a fight soon breaks out as morale falls. When Fowler arrives to restore order, he begins talking of his days in the RAF, leading Ginger to realize that she and the other chickens can build a plane made from Fowler's pictures and personal recollections. The chickens race against time to assemble their plane as Mr. Tweedy works to repair the pie machine. Meanwhile, Rocky comes across a billboard advertising Mrs Tweedy's chicken pies and returns to the farm out of guilt.

The chickens finally finish their plane just as Mr. Tweedy completes the repairs of the pie machine and enters the coop to grab all the chickens. The chickens launch an open revolt, tying up and gagging Mr. Tweedy and readying the "crate", which Ginger persuades Fowler to pilot. As the chickens start to take off, Mr. Tweedy gets free and knocks down the ramp. Ginger jumps down while Fowler turns the plane around, knocking Mr. Tweedy unconscious. As Ginger struggles to lift the ramp, Mrs. Tweedy arrives with an ax and attacks Ginger.

However, Rocky, having had a change of heart, flies over the fence and hits Mrs. Tweedy in her face aboard a tricycle. Rocky and Ginger grab onto a string of lights caught on the plane's landing gear. Mrs. Tweedy awakens, and grabs onto the lights, weighing down the crate. Ginger heads down the string to cut it, but loses the scissors. Realizing the only way to cut the lights, Ginger tricks Mrs. Tweedy by using the hatchet to sever the string. Mrs. Tweedy falls, crashing into the pie machine and plugging her into the safety valve. This causes the machine to explode, destroying the barn and covering most of the farm with a cloud of mushroom gravy.

The chickens celebrate their victory after defeating the Tweedys while Ginger and Rocky kiss, and they fly to an island bird sanctuary where they make their home. Sometime later, the chickens have settled into their new home, and Rocky and Ginger have started a romantic relationship. Nick and Fetcher, two rats that have been helping the chickens throughout the escape, decide to set up their own egg farm, but they fall into a circular debate over whether they must use a chicken or egg to start it.