HOUSTON - A US Air Force instructor on Thursday pleaded guilty to having illicit relationships with two female trainees amid a widespread sex scandal that rocked an Air Force training center.

Staff Sgt. Christopher Jackson was charged with having sex with the women while they were in technical training schools at Lackland and Joint Base San Antonio-Fort Sam Houston, as well as having improper personal relationships with them, according to local TV channel ABC13.

Jackson faces up to one year in prison and a bad-conduct discharge, the report said.

Jackson is one of more than a dozen instructors being investigated as part of the sex scandal that has rocked Lackland, an Air Force base located in San Antonio, Texas, which graduates more than 36,000 airmen annually.

The Air Force had said 28 instructors were caught in the sex scandal that came to light a year ago, with 54 female trainees listed as victims.

Five boot camp instructors have been convicted in courts-martial since last summer and seven more cases are headed to courts-martial.