SAN ANTONIO --  A U.S. Air Force basic training instructor was sentenced to 30 days in jail on Thursday and had his rank reduced after being convicted of improper sexual misconduct at a court martial, one of seven cases in the worst military sex scandal since 1996.

Tech. Sgt. Christopher Smith, 33, received his punishment after the seven-member jury deliberated for five hours. The sentencing, which capped a three-day court-martial at the base, includes a reduction in rank to airman first class.

Smith was convicted Wednesday of seeking to develop an intimate relationship with one female trainee and fraternizing with another at Lackland Air Force Base in San Antonio. He was acquitted of making sexual advances on the female trainee he pursued and of obstructing justice.

Lackland is where all Air Force recruits go through basic training. It has about 500 instructors for about 35,000 airmen who graduate every year. While one in five recruits are women, most instructors are men.

Seven trainers at Lackland have been charged with sexual misconduct.  The latest, Staff Sergeant Jason Manko, was charged on Thursday, Air Force officials said.

Last month, a military jury gave Staff Sgt. Luis Walker a 20-year sentence after the former instructor was convicted of rape and sexual assault. The counts against Walker were the most severe in the investigation.

A third trainer earlier pleaded guilty to sexual misconduct.

Smith can remain in the military after he finishes his sentence, though not as a military training instructor.

A total of 38 women have come forward to claim they were victims of inappropriate conduct at the hands of their basic training instructors.

Courts-martial have been set for three more trainers, with Master Sgt. Jamey Crawford scheduled for trial Sept. 5. He stands accused of having a wrongful sexual relationship with a trainee, wrongfully providing and consuming alcohol with a trainee and committing adultery with the trainee.

In a mixed verdict, a jury found Smith guilty of seeking to develop an intimate relationship with a teenage trainee, but cleared him of charges of making sexual advances. Smith was found guilty of having a personal social relationship with a second female trainee.

Smith was convicted by a "special" court martial, a streamlined process allowed in cases where the maximum penalty is no more than a year in prison.

U.S. Senator John Cornyn, who had blocked the nomination of the proposed Air Force chief of staff over concerns about the sex scandal, said on Thursday he has lifted his hold on the appointment of General Mark Welsh.

The Texas Republican said he asked Welsh to conduct a formal review of current Air Force policy and training on sexual assault prevention and inappropriate relationships.

Petition

U.S. Representative Jackie Speier has called for hearings in the House, saying the problem of women in the military being sexually harassed and raped by men in command positions is far more widespread than officials have been willing to believe.

Pressure is mounting from the public as well.

Paula Coughlin-Puopolo, the former Navy helicopter pilot who exposed the 1991 Tailhook scandal involving allegations of sexual abuse by military pilots, on Thursday presented petitions signed by more than 10,000 people to House Armed Services Committee Chairman Buck McKeon, demanding public hearings into the Lackland case.

The U.S. military hasn't been confronted with a sex scandal of similar scope since 1996. That scandal involved an Army base in Maryland.

Reuters and The Associated Press contributed to this report.

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