Chronic health problems such as cardiovascular disease, diabetes, obesity, cancer and kidney disease account for more than 75% of the nation's $2.7 trillion in annual spending for medical care, says Ursula Bauer of the Centers for Disease Control and Prevention.
He might need to have one while waiting for a TS clearance to go thru. They take from 1-4 months for the interim, the TS clearance could take from 1 month to 2 years from what I have seen. I had to wait 2 years for the final one to go thru. As I said I have also seen people get them really fast too.
This number essentially proves that you have been pre-approved by the US Customs and Border Protection and deemed a low-risk traveler. Once you receive your KTN, you'll be able to swish on by long security lines at 120 airports and get into the specially designated TSA PreCheck line. Skip some common security checks, keep your shoes and belt on, keep your laptop in your carry on, and try not to gloat. TSA PreCheck approval lasts for five years.