The U18 coach has stepped up after Monday's dismissal of manager Ruben Amorim.
The Scot and former United manager Ferguson are close and he revealed on Tuesday: "I don't like to make any major decisions without speaking to Sir Alex.
"I've got a really good relationship with Sir Alex, so I wanted to speak to him first and ultimately to get his blessing, to be perfectly honest with you. I think he deserves that respect.
"I wanted to run it by him and he echoed my thoughts. When you're an employee of the club, it's your job to do your best for Manchester United. It is something I try and live and believe every day, so it was comforting for me for him to say that."
Fletcher admits he hasn't had contact with Amorim this week.
"I've reached out to him but not managed to make contact yet, which is understandable. He's obviously got a lot on in his mind and I've been really busy," Fletcher said ahead of tonight's game with Burnley.
"I'd love to because I had a good relationship with Ruben and he was great with me.
"But it's important you move on very quickly. Football is a cruel game, so it's important we tried to create a little bit of energy and a little bit of spirit. Hopefully there's more of it again tomorrow."