We did this going to Northern Cyprus in October. The journey from Fethiye to Antalya take about 3 and half hours, so if you get the 8 am bus, you'll get in around 11.30, the airport buses leave on the half hour, it's the number 600 and it goes from just around the corner from where you arrive. If you speak nicely to your Fethiye driver he may put his foot down to get you there in time for the connection. Trip to the airport takes around 45 / 50 minutes. Good luck.