The low-fare carrier will continue to serve O'Hare, but Midway will become its primary Chicago airport.
The airline is also adding non-stop flights to 10 new locations, including Atlanta, Denver and Las Vegas.
Inside Chicago O'Hare Airport $8.5B revamp
To celebrate, Frontier is offering flights starting as low as $29 to some major cities.
Airlines have struggled during the pandemic, and now that passengers are flying once again- having more options is encouraging news.
A news conference to celebrate the official first flights out of Midway will take place at 11 a.m.