The United Airlines CEO who suffered a heart attack is coming back

United Airlines CEO Oscar Munoz will return from medical leave the first quarter of 2016.

The airline chief executive has been away from his job since suffering a heart attack in October.

In his absence, the airline has been guided by acting CEO Brett Hard.

Munoz was appointed United Airlines president and CEO in early September after long-time chief executive Jeff Smisek resigned from the company as a result of a federal corruption investigation.

Before taking the top job at United, Munoz was president and chief operating officer for CSX Transportation.

During the third quarter, United Airlines' revenue fell 2.4% to $10.3 billion- falling short of analysts' projections.

Here's Munoz's complete letter:

Dear United team,

Thank you for all the thoughts and prayers you sent to my family and me over the past few weeks. I am excited to tell you that I am on the road to recovery. My time away will be a little longer than I would like, but based upon discussion with my doctors I will be back in the first quarter.

I'm personally grateful to Brett and the entire management team for their leadership and for embracing United's new direction. I know each one of you is committed to achieving our full potential, continuing to focus on building and delivering our shared purpose of making United not only the best airline to fly, but also the best place to work.

While I have been part of the United family for only a short time, I've built many valued and strong relationships so far, and I can't wait to come back.

As I'm sure you can appreciate, this has been a difficult time for me and my family. Your messages of encouragement have helped profoundly. I look forward to seeing you in 2016 to continue working together to build a great airline.

Sincerely,

Oscar