Not quite as quickly afterwards as people remember. All the 9/11 hijackers were dead before the letters were mailed, of course.
After the 9-11 attacks, planes were grounded for days and mail delivery was disrupted.
It made more sense to “wait” to mail them as a “stage 2” attack.
If it wasn’t the 9-11 cells activity, why hasn’t there been a subsequent attack on a national scale by similar opportunists (who literally had days to mobilize their plan and shift blame to the Islamic terrorists in September 2001)?
Not necessarily. The only thing in evidence is the postmark, not the date they were dropped in the mail. Nor do we know when the letters were prepared for mailing
OF course the letters were mailed BEFORE the attack, but due to the way single-piece rate handaddressed letter mail is normally handled by USPS it ended up taking the long route from Boca Raton FL to Central New Jersey.