With the rapid emergence of peer-to-peer applications, more and more applications will generate many-to-one rather than one-to-one traffic flows. While a number of previous works have reported the measured characteristics of available network bandwidth, these measurements are primarily conducted for one-to-one flows or for a physical network link. This paper addresses this void by reporting the characteristics of aggregate available bandwidth in many-to-one data flows over TCP. Based on extensive measurements conducted in the PlanetLab and public FTP servers, we analyze the statistical properties of aggregate data flows originating from multiple senders destined to the same receiver. Our results show that many-to-one data flows exhibit substantially more consistent statistical properties over a long time scale, and thus could open a new way to achieve probabilistic performance guarantees in multimedia applications.