Aasher Liles took the remarkable picture using stunned mum Kerri’s mobile phone.
People have said the shape resembles the cartoon character Casper the Friendly Ghost.
When Kerri took back her phone and scrolled through the images she saw the figure, which she is now convinced is her son’s “guardian angel”.
She said: “I do believe that he captured his angel out the window that day.”
Photographer Kerri said on Facebook: “We were flying back to Houston from Washington and my seven-year-old, who’s recently become obsessed with taking pictures with our cellphones, wanted to take some pictures out of the window after I had reached across him to take one myself.
“As I was deleting, I came across this one close to the middle of all of his cloud and plane wing pics.”
Aasher, who has Down’s Syndrome, was given two As at the start of his name to represent his extra chromosome, as his mum explains.
She said: “His name reflects his AAwesomeness.
“You know when you get an ‘A’ on a paper and how great that is, but when you get an “A+”, that’s really, really good.
“That’s how we feel about AAsher and how we want others to view him and his diagnosis.
“Down’s syndrome is not bad or scary. It’s just a different path than we had planned on taking. We really won the lottery!
“I do believe that he captured his angel out the window that day to bring him comfort in a rather bumpy takeoff.”