What types of airplanes do sky writing?

monoplanes

ANSWER 2

any plane that is certified for aerobatics can do skywriting - a plane not certified for aerobatics cannot legally perform the maneuvers necessary to skywrite although that doesnt stop some pilots - although some experimental classification aircraft can do aerobatics they are limited where they can fly and perform so usually arent used for skywriting - some small low power aircraft are used such as the piper super cub and cessna 150/152, older biplanes are commonly used like the Boeing stearman and dehavilland tiger moth, modern high performance aerobats like the pitts and extra 300, and even converted cessna 172's have been used