I cannot confirm their authenticity, but this archive has United Airlines press releases from throughout the day on 9/11/2001.
It is odd to me that by 11:17 a.m., Flight 93 was reported to have crashed, while United was only "deeply concerned" about Flight 175.
In the press release of 11:53 a.m., United said it was sending a team to Johnstown , PA for Flight 93, to assist in the investigation and help family members, but said nothing about sending a team anywhere for Flight 175. The 11:53 press release said that United had confirmed that both planes had crashed, but did not say where Flight 175 had crashed.
In the press release of 2:09 p.m., United was saying it had "confirmed the loss of [Flight 175]. Last radar contact with the aircraft was between Newark, NJ, and Philadelphia, PA." United also said it was sending a team to New York:
Based on information received from the authorities, United is also sending employees to the New York City area to assist in every way it can with this tragedy.
Even at 5:23 PM, United Airlines was still saying only that it had confirmed the loss of the aircraft and was sending people to New York based on information received from authorities.
It seems almost as if United did not know or did not agree that Flight 175 had hit the South Tower, and was sending employees to New York based only on what the authorities were saying.
The 9/11 Commission Report says that United Airlines headquarters knew at 9:20 a.m. that Flight 175 had hit the South Tower. The 9/11 Commission Report says a lot of things. Perhaps it is true that United Airlines was told at 9:20 that Flight 175 had hit the South Tower, and perhaps United Airlines had some reason for not saying two hours and even eight hours later that Flight 175 had hit the South Tower.