New software for screening travelers at U.S. airports will do away with naked images, addressing a major public concern, the Transportation Security Administration said on Wednesday.

After complaints from travelers the TSA earlier this year began testing at four airports software for the full-body scanners that instead uses a generic body outline and highlights the area where any anomaly is detected, eliminating the actual image of the passenger.

TSA has increasingly relied on the full-body scanners after a Nigerian man allegedly tried to detonate a bomb hidden in his underwear aboard a transatlantic flight in December 2009. The bomb failed to fully explode but set off a rush to upgrade security to detect explosives underneath clothing.

Software upgrades to the 241-mm wave body-scanning machines made by L-3 Communications , will be deployed over the next several months in the 40 airports where they are used, the TSA said.

This software upgrade enables us to continue providing a high level of security through advanced imaging technology screening, while improving the passenger experience at checkpoints, said TSA Administrator John Pistole.

The agency said it also plans to test similar software later this year for the 247 backscatter scanners that are in 38 airports and made by OSI Systems Inc's Rapiscan Systems unit.

The agency has been scrambling to address complaints about the scanners and physical patdowns of young children and elderly travelers while still meeting the security needs for aviation, a prime target of al Qaeda militants.

Later this year, TSA plans to roll out a pilot program that will allow some frequent fliers at four hub U.S. airports to go through expedited screening, an attempt to shift more toward assessing the risk of the individual flier rather than a one-size fits all security model.

(Reporting by Jeremy Pelofsky, editing by Cynthia Osterman)