Several wireless carriers today said they have made significant strides in restoring cellular coverage in areas decimated by Hurricane Katrina. Both T-Mobile and Verizon Wireless said they have managed to restore some wireless service to flooded New Orleans, and many other areas ravaged by the category 4 Hurricane have been completely brought back on line.

T-Mobile today said that 50% of the greater New Orleans area now has cellphone service though downtown still has limited coverage. Meanwhile Verizon has restored service to Louis Armstrong Airport. Both those companies and Cingular and Sprint have also deployed dozens of Cells on Wheels (COWs), generator-powered cell sites with satellite backhaul, primarily to help power the phones of emergency workers.

T-Mobile added that it has managed to bring cell service in Mobile, Ala., up to 80% of its usual strength, and 40% in Hattiesburg, Miss. The major problem with turning up networks is the power outages suffered in most of the regions. Many cellsites do not have permanent generators and the operators have begun deploying emergency generators to run the sites until the power grid is restored.

Also hindering the restoration effort is the lack of accessibility to critical sites. Work crews are not able to get to cell sites and switching centers, especially in New Orleans. While much of the infrastructure is designed to survive storms and submerging, several parts of the network are still underwater and can’t be re-activated until flood waters recede.

Earlier this week Sprint said one of its primary long-distance switches was in an area of New Orleans below sea level and was submerged, forcing the company to take it off line. T-Mobile, however, managed to keep its New Orleans switching facility online throughout the Hurricane and its aftermath. The facility was never flooded and T-Mobile has been airlifting into the facility technicians, supplies and diesel fuel to power its generator.