What are you doing here?
string zbor = fl.ToString();
string companie = fl.ToString();
string aeroport = fl.ToString();
f1 is a string element in fly, so it looks like you need to split it on some parameters first, and then call f1 etc. f1 should only be a single element as it is now.
You should rather make a class called Fly, with zbor, company and aroport as properties, and add this calss in a list. That way you could loop throug the list and simply call it like: