Yes, when George H. W. Bush became a pilot, on June 9, 1943, 5 days before his 19th birthday, he was briefly the youngest pilot in the US Navy.
However, a month later, Chuck Downey became a pilot on July 16, 1943, 17 days before his 19th birthday, taking over the record.
On Friday, 89-year-old Chuck Downey sat down with President George H.W. Bush and his wife, Barbara Bush, at their home in College Station, Texas, Downey said. “In 1942, we both went through training in our 18th year,” Downey said.
For decades after that, Bush thought he was the youngest pilot during the war — earning his wings five days before his 19th birthday.
But while he was vice president, a military magazine put out a call looking to see if there was any younger pilot than Bush. There was, it turned out: Downey became a pilot 17 days before his 19th birthday and wrote the magazine a letter.
And when he heard the news, Bush sent Downey a letter acknowledging his record had been beaten, Downey said.
Daytona Beach News Journal: 'DeLand WWII aviator meets former president' (Anthony DeFeo, Posted Feb 2, 2014)
See also: Google Books. Central Florida's World War II Veterans.
However, there were younger pilots outside the US fighting in World War II.
On the British side, there was Thomas Dobney, who got his wings when he was 15 after lying about his age.
On the Japanese side, Yukio Araki was 17 when he embarked on his final mission: to kamikaze his plane into the USS Braine on May 27, 1945. According to Wikipedia this makes him "one of the youngest kamikaze pilots of World War II."