code: public FlightInfoExtendedBuilder addFlightInfo(String flightNumber,
  			String connectionId, String segmentId, TravelClass travelClass) {
  		return new FlightInfoExtendedBuilder(this, flightNumber, connectionId,
  				segmentId, travelClass);
  	}
docs: Adds a {@link FlightInfoExtended} object to this template. This object is
  mandatory and can't be null for Airline templates. There can be multiple
  flight info object but there must be at least one.
  
  @param flightNumber
  the flight number. It can't be empty.
  @param connectionId
  the connection ID, used to group together segments. It can't
  be empty.
  @param segmentId
  the segment ID. It must match the segment ID.
  @param travelClass
  the travel class. It can't be null.
  @return a builder for the {@link FlightInfoExtended} object.