A federal court is supporting regulators' efforts to make it easier for people to switch phone carriers by allowing customers to keep their phone numbers.

A federal appeals court on Tuesday upheld a Federal Communications Commission rule requiring landline phone companies to allow customers take their phone numbers with them when they switch to a wireless service.

The ruling comes as the FCC is poised to shorten the time period it takes to "port" a customer's phone number from one carrier to another. The current standard is four days.

A shorter wait time would spur competition in an industry heavily influenced by big incumbents, advocates argue. They say people are reluctant to switch to a competitor phone company if they must wait a week or more to receive calls from their old number.

The economic crisis gives new urgency to the issue as more people are considering switching phone carriers or cutting their landline service to save money.

Telecommunications companies seeking a shortened interval are asking for a 24-hour standard but the FCC appears more likely to adopt a 48-hour rule, according to people familiar with the discussions.

The FCC is slated to vote on the number porting item at its May 13 meeting.

The FCC began its rulemaking on phone number porting in 1996, when it required local phone companies to allow customers to keep their phone numbers if they switched carriers and stayed in the same location.

In 2003, the FCC expanded the porting requirement to include people who "cut the cord" by shutting off their landline phones in favor of a cellular service.

The National Telephone Cooperative Association, a group of small rural phone companies, challenged the rule. NTCA said the number porting requirement unduly burdens its members who bear high interconnection costs when transferring calls to cellular providers.

The three-judge panel rejected NTCA's claims, noting that rural carriers' disproportionate interconnection costs aren't unique to phone number porting. The FCC is addressing that problem in a larger policy discussion on how phone carriers pay each other to transfer calls, the court noted.

Small phone companies like Windstream Corp. (WIN) also are telling the FCC that shortening the number porting period would be too costly for them.

The FCC is considering waiving a shortened porting period for small carriers, but larger carriers like AT&T Inc. (T) and Verizon Communications Inc. (VZ) now are arguing that any new standard should apply to all carriers, regardless of their status.

Rep. Rick Boucher, D-Va., who chairs a telecommunications subcommittee in the House, has asked the FCC to consider ways that small carriers can be compensated for the extra expense of a quick phone number transfer.

-By Fawn Johnson, Dow Jones Newswires; 202-862-9263; fawn.johnson@dowjones.com