NASA astronaut Nick Hague and Roscosmos cosmonaut Alexandr Gorbunov arrived in Florida on Saturday afternoon ahead of their final launch preparations. A flight readiness review occurred on Monday, Sept. 23.

A Russian Soyuz booster arrived at its launch pad on the Kazakh steppe Sunday, the last stop before liftoff Wednesday with a three-person crew bound for the International Space Station.

The problem for NASA and Boeing is that the Starliner’s service module, which houses the helium lines, thrusters and other critical systems, is discarded before re-entry and burns up in the atmosphere. Engineers will not be able to study the hardware after the fact and as a result, they want to collect as much data as possible before NASA astronauts Butch Wilmore and Sunita Williams head home.