The hospital who placed it should give you a credit-card sized card that indicates the device. Have it in your dad's wallet, plus the letter.

Absolutely do not let them even touch the catheter. If it were me I would choose not to fly. I shudder to think what is on their gloves.

Not sure which airports they are going through but it would be even better to have them go through regular metal detector and avoid the entire problem. PICCs are non-metal and should not alarm the WTMD.