Launch from Cape Canaveral (KSC); landing on Cape Canaveral (KSC); ISS-19-12A ITS-P3 / ITS-P4.

The mission delivered the second port-side truss segment (ITS P3/P4), a pair of solar arrays (2A and 4A), and batteries. A total of three spacewalks were performed, during which the crew connected the systems on the installed trusses, prepared them for deployment, and did other maintenance work on the station.

For the first time, NASA managers decided to move the STS-115 launch date forward to August 27, 2006 to obtain better lighting conditions to photograph the external tank.

About half an hour before the scheduled launch time, NASA announced it had decided to delay the launch for another 24 hours while the fuel was drained out of the external tank and the problem assessed. The sensor in question, ECO sensor No. 3, was proved to be faulty when it indicated that there was still liquid hydrogen in the external tank despite all of it being drained out. The other three ECO sensors correctly indicated a dry tank; and as long as they didn't start to malfunction, NASA could allow a launch with three out of the four ECO sensors operational.

Following a two days solo flight the Atlantis docked to the ISS on September 11, 2006. During the next six days the crew performed common work with the ISS expedition 13. The launch was scrubbed several times because of bad weather and technical problems. It was the first time in almost four years that a major new space station component, the 17.5-ton, bus-sized P3/P4 integrated truss section, has been launched.

The first EVA was performed by Joseph Tanner and Heidemarie Stefanyshyn-Piper on September 12, 2006 (6h 26m) for installation of power and data cables between the P1 and P3/P4 structures in preparation for solar array deployment.

The second EVA by Daniel Burbank and Steven MacLean occured on September 13, 2006 (7h 11m) to continue work to prepare the International Space Station’s P3/P4 integrated truss for operation; StevenMacLean became the first Canadian to perform an EVA.

The third and final EVA by Joseph Tanner and Heidemarie Stefanyshyn-Piper was performed on September 15, 2006 (6h 42m) to perform final tasks required for activation of the Solar Alpha Rotary Joint (SARJ). The SARJ is an automobile-sized joint that will allow the station's solar arrays to turn and point toward the sun; they also prepared the P3/P4 truss and its solar arrays for operation by setting the stage for deployment of the truss' radiator. Joseph Tanner has performed than 7 EVA's in his career. Later on the solar arrays were fully unfolded. Heidemarie Stefanyshyn-Piper retrieved the materials on the International Space Station Experiment 5. The materials science experiment tests the effects of the space environment on prospective spacecraft materials.

Other work of the crew were: a talk of Steven MacLean with the Canadian Prime Minister Stephen Harper and other press meetings, transferring cargo, including water, between the shuttle and the space station, removal of the REBA, Rechargeable EVA Battery Assembly, photo shootings

After undocking from the ISS, the heat shield was inspected; additional inspections were necessary, when a video from cameras aboard the shuttle showed a piece of debris in close proximity to the vehicle, but engineers found no issues of concern during the survey.