//returns if there is flight restrictions from one country to another
        public static bool HasRestriction(
            Country from,
            Country to,
            DateTime date,
            FlightRestriction.RestrictionType type)
        {
            FlightRestriction restriction =
                GetRestrictions()
                    .Find(
                        r =>
                        (r.From == from || (r.From is Union && ((Union) r.From).IsMember(from, date)))
                        && (r.To == to || (r.To is Union && ((Union) r.To).IsMember(to, date)))
                        && (date >= r.StartDate && date <= r.EndDate) && r.Type == type);

            //FlightRestriction res = GetRestrictions().Find(r => r.From == from && r.To == to && r.Type == type);

            return restriction != null;
        }
 public static void AddRestriction(FlightRestriction restriction)
 {
     Restrictions.Add(restriction);
 }