Passenger Ben Pedraza who wound up next to Landon for the long flight, sent a message to his mum to let her know her son was alright and not trouble at all.
He shared a photo of the two of them on their way, to calm the mother's worries.
"He did ask if we were there yet several times but he was a great travel buddy," Pedraza wrote. "We had a good time and played a few rounds of rock-paper-scissors. He's a great kid and you're a lucky mom.
Bjornson took the message and posted it on Facebook thanking Pedraza for looking after her son.
Pedraza told KATU that Landon had been no trouble. The pair had hit it off instantly over a shared sense of humour although "after a while, he asked me to quit making dad jokes," he said.
The cute travel couple and the heart-warming story were a big hit online. Bjornson's post had over 118,000 shares via Facebook and many messages of support.
"I am so grateful to this individual," she wrote. "There are still kind people in the world who make a difference."
As for the $10 note, Pedraza said he donated it to the US charity autism-society.org.