CHICAGO — The federal government is quietly removing full-body X-ray scanners from seven major airports and replacing them with a different type of machine that produces a cartoon-like outline instead of the naked images that have been compared to a virtual strip search.

The Transportation Security Administration says it is making the switch in technology to speed up lines at crowded airports, not to ease passenger privacy concerns. But civil liberties groups hope the change signals that the equipment will eventually go to the scrap heap.

The machines will not be retired. They are being moved to smaller airports while Congress presses the TSA to adopt stronger privacy safeguards on all of its imaging equipment.

The machines are being pulled out of New York's LaGuardia and Kennedy airports, Chicago's O'Hare, Los Angeles International and Boston Logan, as well as airports in Charlotte, N.C., and Orlando, Fla.

The TSA would not comment on whether it planned to remove machines from any other locations.