History: Jacqueline Falsworth was the daughter of the British aristocrat, Montgomery, Lord Falsworth, who had been known during World War I as the costumed champion Union Jack. In early 1942, Jacqueline was serving in Britain's Home Guard, a civil defense group, when she was attacked by the vampire Baron Blood, an agent of Nazi Germany. Unknown to Jacqueline at this time, Baron Blood was actually her own uncle, Lord John Falsworth. Baron Blood was forced to flee by the original Human Torch, who took Jacqueline to her home, Falsworth Manor, where the Torch met her father. Lord Falsworth and Jacqueline befriended the Torch and his fellow members of the Invaders, a team of costumed adventurers who battled the Axis powers on behalf of the Allies during World War II.

Subsequently, Baron Blood abducted Jacqueline but was defeated by Union Jack and the Invader Captain America. Suffering from a great loss of blood from being bitten by Baron Blood, Jacqueline was rushed to a hospital by the Invaders. There she received an emergency transfusion of blood from the original Human Torch, an android. While she was recovering, the Nazi agent called the Blue Bullet attacked the hospital in search of the Invaders. To her surprise, the still-recuperating Jacqueline discovered that she now had the ability to move at superhuman speed. She courageously used her new power to save the Human's Torch's life from the Blue Bullet's attack. The Blue Bullet was then defeated by another Invader, the Sub-Mariner.

Jacqueline discovered that as a result of the combination of a foreign element introduced into her bloodstream by Baron Blood's bites and the artificial blood given her by the android Human Torch, she had developed the ability to move at superhuman speed and exceptional metabolic vitality. (Possibly the android blood and the element introduced into her bloodstream by Baron Blood had actually jointly activated latent mutations in Jacqueline, thus giving her these superhuman capabilities.) Following her complete recovery from her injuries, Jacqueline made herself a costume, took the name Spitfire (after the British war planes of the period), and volunteered for Invaders membership. She was accepted into the team. Spitfire fought alongside the Invaders, including her brother, the second Union Jack, while the group was in the European Theater of Operations. At the war's end she retired as a costumed adventurer.

Jacqueline's superhuman capabilities gradually faded as her body slowly eliminated the foreign elements that had given them to her. Her superhuman abilities had entirely vanished by 1950. In 1956 she married the British nobleman Lord Crichton. They subsequently had a son, Kenneth. Lady Crichton, as she is now known, moved back to Falsworth Manor to care for her aged father, who died a year after her return there. Lady Crichton continues to live in retirement at Falsworth Manor.

Later, Jacqueline helped assemble Namorita, Captain America and Union Jack to aid the former Invaders, the original Human Torch and the Sub-Mariner, who were captured by the latest incarnation of the Nazi villain, Master Man. In attempting to rescue their ally, Jacqueline was mortally wounded. After yet another emergency blood transfusion from the android Human Torch, Jacqueline's metabolism returned to super human levels and her Spitfire powers have reactivated. A side effect of her returning powers caused her to become young again, as she reverted to the body of a 16 year-old. Nevertheless, Jacqueline returned to her home at Crichton Manor.

Height: 5 ft. 4 in.
Weight: (as Spitfire) 110 lbs. (as older Jacqueline Falsworth Crichton) 140 lbs.
Eyes: Blue
Hair: Blond

Strength Level: As Spitfire Jacqueline Falsworth possessed superhuman strength primarily in her lower body as part of her body's adaptations for running at superhuman speed. She could leg press approximately 550 lbs. under optimal conditions. With her upper body she could lift (press) slightly more than an ordinary human woman of her age, height, and build who engaged in intensive regular exercise could. Without her superhuman powers Jacqueline Crichton today possesses the normal human strength of a woman of her age, height, and build who engages in moderate regular: exercise.

Known Superhuman Powers: As Spitfire, Jacqueline Falsworth possessed the ability to move at superhuman speed and superhuman metabolic vitality. She could run at her top speed of 50 miles per hour for up to a half hour before fatigue impaired her performance. At lesser levels of exertion, she could function optimally for hours.

Spitfire's entire body was oriented toward the rigors of high-speed running. Her cardiovascular and respiratory systems were more efficient than a normal woman’s. She metabolized an estimated 50% of the caloric energy content of foodstuffs (normal human use is about 25%). The chemical processes of Spitfire's body were so highly enhanced that her body did not generate fatigue-poisons, the normal by-products of locomotion which force the body to rest, as quickly as a normal human being does. Her tendons and bones somehow became stronger in order to withstand the stresses of high speed motion, and her joints were smoother and lubricated more efficiently than a normal woman's. Spitfire's heightened metabolism afforded her great resilience to impact related injuries. Her reaction time was about twice as fast as that of a normal woman.

Other Abilities: Spitfire was an exceptional natural athlete and fighter, trained by Captain America in several forms of hand-to-hand.