Some Wold Newton sites advance the notion that The Phantom Lady (Sandra Knight) and the Invisible Scarlet O'Neil (AKA The Invisible Woman and presumably elsewhere known as "Starlet O'Neil") were the same person and I have written on the subject before. When I mentioned it before I thought it unlikely, however now I am prepared to say that the idea is likely to have more merit to it than I had originally thought. Jess Nevins has an alternate proposal: he says that Miss America was The Invisible Scarlet O'Neil.
Actually this is more tangled than it might seem because the Miss Americas (several) were actually a subsection of the Wonder Women and new candidates were elected annually: and the Phantom Ladies were a splinter line from the line of The Phantoms and were simultaneously also Supergirls before the existence of Supergirl was officially revealed. And the main Phantom Lady was none other than "Mary Marvel" - it's complicated. Here is Jess Nevins' statement on Miss America:
“Miss America”“Miss America,” in the Timely comics, was a woman who was in a lighthouse when it was struck by lighting and so gained a variety of powers. This very comic book creation origin would not work in reality, of course. A woman struck by lighting, or in a building struck by lighting, would simply be shocked, injured, or killed. Needless to say, there was no “Miss America.” There was, however, a woman with an extraordinary ability who fought against the Axis. Her name was Scarlet O’Neil, and she was an extremely potent weapon for the Allies. Her story actually begins with her father, Dr. Terence O’Neil. O’Neil, a native of Boston, grew up in that city’s South End, the Irish enclave of the city. He attended Harvard and MIT and earned two Ph.D.s by age 24. He married Eileen O’Flaherty, his high school sweetheart at 25, and she gave birth to two daughters, Scarlet and Nora, the following year, in 1920. However, their marriage abruptly disintegrated in 1921 following the signing of the Anglo-Irish Treaty. Eileen was, like Terence, of Irish descent, and both felt strongly about Irish independence, having funneled money to the Irish Republican Brotherhood during the 1916 Easter uprising. However, Terence was more naturally moderate and felt that the Anglo-Irish Treaty, which gave Ireland limited self-government, was the best that Ireland could hope to achieve. Eileen felt that the Treaty was a betrayal of the cause. Terence and Eileen’s disagreements on this issue became increasingly heated and poisonous, until she finally left him and went to Ireland. She took Nora with her, and raised her to become a “freedom fighter” for the Irish Republican Army. Nora later became known as “Lady Nora O’Neil,” and was one of the most feared Irish terrorists. Terence raised Scarlet to be everything her mother was not: moderate, caring more for justice than for more selfish principles, and thinking of herself as an American, not an Irishwoman in America. Terence meanwhile concentrated on making weapons and technology for America, at some point becoming a member of the “Spindrift Island” coalition of scientists. (He was known there as “Dr. Wisecarver”) In 1940 Terence was working on perfecting a ray which would turn its targets invisible when Scarlet stuck her finger into the ray’s beam. The interruption in the ray gave Scarlet the ability to turn invisible but unfortunately created a feedback loop which destroyed the ray. Terence was never able to reconstruct the ray or make a working duplicate, and so was left with Scarlet instead of an army of invisible agents. She, patriotic to the core, volunteered her services in the fight against the Axis, and used her abilities to fight spies in the US and the enemy on its own ground. Like most of the other figures in this article, “Invisible Scarlet” O’Neil’s activities during the war remain Classified. However, rumors spread during the War about mysterious “angels of mercy” who helped American and Allied troops at odd times, especially during the invasion of Europe in 1944, and Stan Lee would undoubtedly have heard these rumors. Lee probably turned this image of a female “angel of mercy” into the superheroine “Miss America.”
Scarlet O' Neil was one of the "Spy Shadow" agents that operated by use of Astral Projection.
"Scarlet" was also a reference to her original; version "Supersuit" which was all-red and in fact was a "Marvel" costume (also used in another variation as the "Blonde Phantom": Blonde Phantom" and "Phantom Lady" were more or less "Supergirl Red and Supergirl Blue")
Below is the "Supergirl" costume of the 1940s
"Mary Marvel" was symbiotic with the blonde "Supergirl" who was actually Loana the Cavewoman. "Mary Marvel" was the one elsewhere portrayed as "Linda Lee Danvers" Linda Lee was using a skull ring that was handed down from the line of Red Phantoms, as explained on Cedar and Willow previously