Thirty-six U.S. senators have now joined the growing ranks of those who have asked the FCC to do more to stop carriers from failing to complete calls to rural areas.

“Swift action is needed to restore quality service in rural areas and to preserve the basic integrity of our nation’s communications network,” wrote the senators in the letter, which was championed by Senator Tim Johnson (D- S.D.).

The letter makes several specific recommendations to the FCC. If the FCC suspects an originating carrier of violating call completion rules, the senators suggest that the commission should require that carrier to submit network performance data, including a detailed analysis of call completion rates. If that analysis shows that calls to rural areas have greater failure rates, the carrier should be subject to further review of its operations, the letter says.

The letter also recommends that if the commission suspects an originating provider of failing to properly deliver calls to rural areas, the provider should be required to report whether it has used a least cost routing service, which could warrant additional scrutiny.

Rural call completion problems first gained public attention in early 2011 when rural telco groups released the results of a survey showing that 80% of rural carriers reported termination problems. The call completion problem appears to have arisen because per-minute access charges that carriers pay one another for connecting calls to one another’s customers are higher in rural areas to help cover the higher costs of delivering service there. Some originating carriers apparently try to avoid paying these charges by simply failing to complete calls to rural areas – or by handing off calls to a least cost router who fails to complete them.

This isn’t the first time Johnson has spearheaded Senate efforts involving rural call completion. Just under a year ago, Johnson and other senators wrote a letter asking the FCC to take action on call completion. And that letter may have helped persuade the FCC to issue a rural call completion order a month later.

In that order, the FCC said that carriers deliberately failing to complete calls to rural areas could face cease and desist orders, forfeiture, license revocations and fines of up to $1.5 million. But little or no enforcement action has been taken since then and a recent survey conducted by rural telco associations found that 62% of rural telcos have seen call completion problems remain steady or increase since the FCC call completion order was adopted.

At the time the survey results were released, the rural telco associations asked the FCC to do more to stop call completion problems.

The National Association of Rural Utility Commissioners, which represents state commissioners, also urged the FCC recently to do more to prevent carriers from dropping calls to rural areas.

Senate support for further action on call completion appears to be rising. While Johnson’s letter from January 2012 had 23 signatories, the new letter was signed by more than a third of all senators.

Several rural telco groups, including the National Telecommunications Cooperative Association, the Organization for the Promotion and Advancement of Small Telecommunications Companies, and the Western Telecommunications Alliance, issued statements in support of Johnson’s letter.

Instances of calls not completing or resulting in ‘dead air’ are rampant in rural communities and in many cases are getting worse,” said NTCA CEO Shirley Bloomfield in the NTCA statement. “While the FCC’s declaratory ruling nearly 10 months ago was a positive step, it has become obvious that more investigation and actual enforcement is necessary to put an end to the bad practices underlying this problem.”