Shortly after midnight local time in Newfoundland, Canada, the first reports emerged of potential signs of hope.
Two US media outlets reported a leaked internal memo sent to the US Deparment of Homeland Security.
This said a Canadian aircraft had detected underwater "banging sounds" in 30-minute intervals coming from the search area.
"The P8 [seacraft] heard banging sounds in the area every 30 minutes. Four hours later additional sonar was deployed and banging was still heard," Rolling Stone magazine reported the email as saying.
CNN also reported an internal update sent Tuesday night, which suggested more sounds were picked up.
“Additional acoustic feedback was heard and will assist in vectoring surface assets and also indicating continued hope of survivors,” said the second memo according to CNN's report.
An hour after the media reports, the US Coast Guard confirmed that a Canadian search aircraft had picked up "underwater noises".