WHO knows how these things gain momentum on the Internet, but there have been enough online protests against the new body imaging machines at airport checkpoints that the Transportation Security Administration’s new boss, John S. Pistole, called me on Monday to talk.

Mr. Pistole was specifically worried about the Internet-based campaign encouraging fliers who opposed the new machines to observe a “national opt-out day” on Nov. 24, the day before Thanksgiving. Any passenger can opt out of a scan that creates an image of the naked body and choose a full-body pat down instead. Only a tiny percentage of passengers now do, the T.S.A. says. But if enough people choose to do so on one of the busiest travel days of the year, checkpoints could become crowded and disorderly.

As any security expert knows, a chaotic checkpoint is a security problem. “If terrorists can anticipate that, it gives them an opportunity” to try to evade various layers of security by creating an incident for diversion, Mr. Pistole said. “And what would this do for travel plans for Thanksgiving? Are people going to miss flights because there are long backups, because other people are protesting?”

As if that were not trouble enough, some airline pilots are engaged in their own protests against the body imagers, which the T.S.A. is now calling advanced imaging technology. Pilots have long bristled at being subjected to intensive security when, as they point out, a pilot in control of an airplane does not need a Swiss Army knife to bring it down. Last week, the union representing 11,500 pilots at American Airlines called on members to “politely decline” screening by the “backscatter” models of the machines, the models that use X-ray technology.