https://www.chabad.org/library/article_cdo/aid/3834226/jewish/What-Is-the-Amidah.htm

This true significance of 19 is likely because the Jewish faith is based on the moon. And the moon has a 19 year cycle. Thus why the Hebrew holidays fall on the same day every 19 years.

And never forget, 19 years after 911 and the 19 hijackers, we got the Covid-19 pandemic.