I've been hopping around Europe for the last few months with flight that I've booked a variety of ways:

Barcelona, Spain to Leipzig, Germany (cash, Vueling)
Prague, Czech Republic to Belgrade, Serbia (Etihad Guest miles, Air Serbia, Anatomy of an Award)
Belgrade to Tivat, Montenegro (cash, Air Serbia)
Sarajevo, Bosnia to Zagreb, Croatia (cash, Croatia Airlines)

Now I have two more flights coming up from Zagreb to Spain and back for a quick trip.