The pair were missing for Wednesday's midweek draw at Cardiff City, but are both in contention for the Hillsborough visit of QPR tomorrow in the Championship.
Striker Fletcher also missed the Owls' 1-0 win at Huddersfield Town on Sunday, but is back in training after a bout of illness.
“He will be available,” said Owls head coach Carlos Carvalhal. “Fletcher trained for the first time yesterday.
“He will train today and check on his energy and our other attackers. We will see who is better to start and can give energy to the team.”
On Bannan, who was rested midweek, Carvalhal added: “He will be ready to be in the squad tomorrow.”
The Owls are also hopeful goalkeeper Keiren Westwood and midfielder Ross Wallace will be fit to play, after both went off injured at Cardiff.
Westwood was taken off in the first half due to a back problem and replaced by rookie Cameron Dawson.
Westwood felt the knock in the warm-up but tried to play on. It is the second time the Republic of Ireland has come off in the last three outings.
Carvalhal explained: “We will see if Keiren recovers or not. We have some wishes he will be okay.
“If he doesn’t recover, it is not a problem as we have trust in all the goalkeepers we have in the club.
“Last season, we put Joe [Wildsmith] in and he did really well. Cammy [Dawson] is good value and Jake [Kean] is ready too.”