This event was essentially unique: no other similar conspicuous flows were observed anywhere else in the Twin Towers or in other buildings affected by the 9/11 attacks.
UPS vs UPS?
The same alteration is mentioned in the NCSTAR1-1C report, on page xlviii, but with a slightly different wording which will turn out to be very significant: instead of referencing "United Parcel Service", it uses only the acronym ("UPS").
"Enrico,modifications were made in 1991 to reinforce the 81st floor of WTC 2 in an area occupied by the United Parcel Service.Modifications were made in 1999 to floor 81 in an area of the floor occupied by Fuji Bank to accommodate the weight of an uninterruptible power supply.Both of these modifications are documented in the section of the NIST WTC Investigation Report known as NCSTAR 1-1C (go to http://wtc.nist.gov/NISTNCSTAR1-1C.pdf).What is perhaps confusing is that both modifications were made to areas where there are two-way trusses (the corners of the building) and the acronyms (UPS for "United Parcel Service" and "uninterruptible power supply") are the same.However, these modifications were made eight years apart for two different tenants, so there is no link between them.I hope this answers your question.Thank you,Michael Newman Spokesman, NIST WTC Investigation "
As regards NIST's statement that United Parcel Service was indeed a tenant of the 81st floor, we are awaiting a clarification from the company.