Sixty-four-year-old Dennis Spangler begged forgiveness from the victims and their families after admitting to indecent assault, indecent exposure and other offenses in Lancaster County Court.
Police say Spangler had sexual contact with the teens between 2007 and 2009 at his Manheim Township home and the Lancaster Airport, where he was a flight instructor.
Spangler retired from the United Methodist Church in 2007. He surrendered his ministerial credentials after charges were filed last September.
Spangler faces 8 to 20 years in prison when he is sentenced. A judge revoked Spangler's bail on Thursday, sending him to Lancaster County Prison.
