Cook bacon until browned, about 8 minutes. Drain on paper towels.
STEP 2
Spread mayonnaise on one side of each bread slice. Layer chicken, Swiss cheese, lettuce, tomato, and bacon on 2 slices (mayonnaise side). Top with other 2 slices, mayonnaise-sides-down.
STEP 3
Heat panini press; coat with cooking spray. Cook sandwiches until heated through and cheese melts, about 7 minutes.