Aviation security leaders are moving forward with plans to shift toward a risk-based system of passenger screening — an idea supported by the travel industry and government officials who want screeners to focus on travelers who may present a security threat.

But as details emerge on how governments and airlines plan to distinguish between “trusted travelers” eligible for lighter screening and those who will receive more scrutiny, civil liberties groups and some European regulators are questioning the use of vast quantities of personal data to decide which travelers to examine more closely — or to prevent from flying at all.