Croatia Airlines. Croatia Airlines is the national airline of Croatia. Through its hub in Zagreb, Croatia Airlines serves 22 destinations in 10 countries in Europe including Austria, Belgium, France, Germany, Italy, Netherlands, Switzerland and the United Kingdom.Earn MileagePlus miles on all qualifying Croatia Airlines flights, as noted in the charts below.You’ll earn miles according to the booking class that you purchase. To receive mileage credit, present your MileagePlus number when you make reservations and make sure that it appears on your boarding pass at check-in.arn MileagePlus miles on all qualifying Croatia Airlines flights, as noted in the charts below. You’ll earn miles according to the booking class that you purchase. To receive mileage credit, present your MileagePlus number when you make reservations and make sure that it appears on your boarding pass at check-in.