The all-stock merger with Phoenix-based Mesa will strengthen the size of Republic's fleet and increase the number of domestic routes the carrier flies.

Republic Airways and Mesa Air Group, two regional airline brands with several decades of history and complementary Embraer fleets, have announced their intent to merge, a transaction both U.S. companies expect will close by year’s end.

Republic Airways and Mesa Air Group Inc. are combining in an all-stock deal that will create a regional airline with access to more planes to service routes. Specific financial terms of the deal weren't disclosed in a statement Monday.