He projects that 50 million people will switch providers in 2004, up from the 39 million the group expects to change carriers this year.

The new rules are likely to reduce the number of unauthorized changes, but could also make it more difficult for consumers to change long-distance carriers.

Because of stiff competition among carriers, many people change carriers and get new phones.

A. The changes could spark more unit sales, because when people change carriers, they frequently need a new phone.

Passengers need to book only one ticket and check in baggage once, regardless of how many times they change carriers.

Wireless carriers are supposed to install technology by late November that will let customers keep their phone numbers when changing carriers.

And the available evidence suggests that consumers would be more likely to change carriers if they could take their phone numbers with them.

Even within the same market, if customers wants to change carriers, they must often acquire a new phone that operates under a different technical standard.

With the transferable service, customers can change long-distance carriers and keep their "800" numbers.

Watch out for reduced baggage allowances when changing carriers or seating classes.