Although decidedly lax in following church teaching on some subjects such as adultery, JFK attended mass regularly. When the family was in Palm Beach, they attended St. Edwards Catholic Church.
JFK sat in a reserved pew with Secret Service men on either side of him. Even in church, he was unobtrusively accompanied by a military officer carrying the codebook that would allow Kennedy to control nuclear launches. In addition, a secure “red phone” was installed in the back of the church that would allow instant communication in the case of a developing crisis.