It was reported back in April that American Airlines was dropping several teams from their charter contracts including the Steelers. Pittsburgh and American had been working together since 2015 when American and United merged.
According to Jill Beckman of the Post-Gazette, the team indicated that Miami Air International is the current charter airline, but they will continue to seek out a more permanent solution after this season.
The team has typically been among the least-traveled teams in the NFL. This season they will fly to Kansas City, Detroit, Chicago, Houston and Indianapolis in addition to their AFC North road games.
(Curt Popejoy - Steelers Wire)