(WHTM) -- If you have seen a United States or Commonwealth flag on Wednesday, you might be wondering why they are flying at half-staff.

In observance of Patriot Day and National Day of Service and Remembrance in honor of those who lost their lives on Wednesday, over two decades ago, on Sept. 11, 2001, Governor Josh Shapiro ordered that all flags to be flown at half-staff.

Flags that are on all state facilities, public buildings and grounds were ordered to fly the flags at half-staff beginning at sunrise and will return to full staff at sunrise on Thursday.

All Pennsylvanians are invited to partake in the tribute.

Sept. 11 was designated as Patriot Day by Congress, and they also requested that Sept. 11 be recognized as National Day of Service and Remembrance.