Flight Cert not enough? You shall use them wisely! The number of FC required to establish a new route is depending only on the numbers of existing routes of both start/target cities. So if you only make 2 routes for each city with proper planning, then you can easily connect all cities without FC in early stage of game. Then you can use FC later to establish Express Route later on.
i've already finished the game before these Kongregate Achievements were added, but now even i've replayed a few levels, seems still cannot got the achievement pointes :(
 "Aviator"){kind=icon}
 "Decision:Medieval"){kind=icon}
 "Symbiosis"){kind=icon}