I've alway thought driving from Los Santos to Liberty City in 5 minute is so unrealistic and also the airport in the game doesn't have many uses so i made this simple mod
Allow you to fly from LS to LC and LC to LS via airport (now include the moved version)
Simply walk to the airport blip and follow the help message
The cost of a flight is $200
Installation:
-Make sure you have ScripthookV and ScripthookVdotnet installed
-Depend on whether you have the original Liberty Rewind or the moved map choose between two version and put the .cs file inside of your script folder
Liberty Rewind: https://drive.google.com/file/d/1H0mDEQ1QweA2G4OFLo4LQrgfBM6ps9Tf/view 
Liberty Rewind moved: https://drive.google.com/file/d/1Y2Pb-R99cjFhXINE3LwrdafBNxIEAy96/view?usp=sharing