Assuming the third place finisher cannot make it to the Worlds for any reason, then the 4th place finisher,(first alternate) takes his place and so on. Are the 4th and 5th place finishers considered actually on the team as backups?
Maybe I was not clear in my previous post. The fourth and fifth place finishers are the first and second alternates for the U.S. Team. Technically, they are not "on the team". Each of these alternates really have no official status on the team other than being recognized as an alternate who would become a Team Member if for some reason a team member cannot participate in the World Championships. That does not mean that the alternates cannot travel with the team as Supporters which is an official status recognized by the AMA and the organizers of the World Championships. But that travel would be as a Supporter, not as an official member of the the team. In the case of CL Aerobatics (F2B), the official team is comprised of the three senior members as well as the Junior member. There is no such thing as an "Official Alternate" as a member of the team.
I hope that I am not making this even more confusing. Anybody who wants to travel to the World Championships with our Team can do so as an "official Supporter". We had approximately 45 such supporters last year in Valladolid which, in addition to our 26 Team Members (F2A, F2B, F2C and F2D) was one of the larger national contingents at the World Championships. There is a Supporter fee charged by the organizers. This gives a pass to the various venues at the Championships, some priority for a banquet ticket and a few other benefits as well as having the Team Managers help arrange for meals and lodging during the dates of the World Championships if so desired.
Also, just for the record, Team Members must make and pay for their own travel arrangements to the World Championships, The AMA pays for the entry fees for the team members which also covers their food and lodging during the official days days of the contest. There is a relatively small allowance from the AMA provided to each Team Member, but it represents only a small fraction of the total cost that a Team Member will have in order to participate in the Championships. What many people do not appreciate is the significant commitment in energy and resources that are required for a Team Member to represent our country in World Championship competitions.