What specific capability did NASA elect to test by returning the Starliner spacecraft solo?

Answer

The vehicle autonomous return capabilities, including re-entry and landing

NASA chose to test the vehicle's autonomous return capabilities, including re-entry and landing, without putting human lives at direct risk for the final phase.

What specific capability did NASA elect to test by returning the Starliner spacecraft solo?

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Boeing's Starliner astronauts could be in space until 2025 - YouTube

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