I have a flight from Athens bound for one of the Greek islands at 5:30 a.m midweek. What time should I plan to get to the airport at that time of the morning? Since trains aren’t running that early, is a taxi the only option to the airport from the central Athens district? I looked up Uber and it says that you can order a taxi through their service. Is it okay to book taxi when I need it at that time of the morning or should I prebook?