Preheat the air fryer to 360°F for 3 minutes.
Separate the biscuits. Stretch each one into an oblong about 5 inches long and 2 inches wide, then press it to an even thickness.
Brush both sides of each bar with melted butter.
Lightly spray the basket. Place 3 to 4 bars in a single layer with space between them.
Air fry at 360°F for 5 to 6 minutes, flipping halfway, until golden brown and puffed. Check at 4 minutes. Repeat with the remaining bars.
While the bars cook, whisk the powdered sugar, maple syrup, maple extract, milk and salt until smooth and thick. Adjust with milk or powdered sugar as needed.
Cool the bars for 2 to 3 minutes. Dip the top of each bar in the glaze, let the excess drip off, and place on a wire rack.
Let the glaze set for about 10 minutes before serving.