There has been nothing I have seen to indicate that the released radiation particles are light enough and have been propelled fast enough to get into the jet stream. We're not dealing with a volcanic eruption or a nuclear detonation. I'll have to leave it at that.

I forgot to mention that these types of radiation detectors, including the drive-through ones in place at various "undisclosed facilities," will routinely detect and alarm on people who have recently undergone radiation treatments for cancer or have had radioactive iodine injected for medical tests. Radioactive iodine has a short half-life, as do most cancer treatment isotopes, but, people who fly within hours or a few days of treatments are often still quite radioactive. This news source didn't bother to investigate that aspect of the story, nor would the DHS even note that this is the most common source of positive hits.