There are 29 9-letter words that start with 'ai'.
Note: These 29 9-letter words that start with 'ai' are found from the USA & Canada version of the tournament Scrabble word list.
Also see words start with air, ail, aid, aim, aig, ais, ait, ain, aik, aio, aiv, aib.
3-letter words start with 'ai' (7)