A medical emergency that occurs during a transit leg — between destinations, away from any facility — is handled by the vessel's medical bay as the first response. The flight surgeon assesses the situation and determines whether the condition can be managed aboard for the remainder of the leg, or whether the vessel needs to divert to the nearest appropriate facility. The captain has final authority over diversion decisions, acting on the flight surgeon's medical recommendation.

The decision to divert is not made lightly. A diversion affects all passengers on board, extends the voyage for everyone, and may result in missed downstream transfer windows. The threshold for diversion is a condition that cannot be safely managed by the medical bay for the expected transit duration and that poses a serious risk to the passenger's life or long-term health if not treated at a higher level of care.

If diversion is recommended, the vessel proceeds to the nearest appropriate facility. During the Moon-to-Mars and Mars-to-Venus legs, this typically means reversing to the last stop or continuing to the next stop — whichever is closer at the time of the emergency. During the outer system legs, the Ceres Waystation maintains a permanent emergency medical dock and is the primary diversion point for emergencies occurring anywhere on the Ceres-to-Enceladus sequence. The Ceres facility is equipped for stabilisation and telemedicine consultation with Earth-based specialists; it can hold a patient for up to 30 days while awaiting a medical repatriation flight.

Insurance coverage for diversion costs — including the cost of the emergency medical repatriation flight from Ceres or another diversion point back to Earth — is covered under standard travel insurance when the emergency is documented by the flight surgeon as a genuine medical emergency. Passengers who are diverted are also entitled to a proportional refund of the unused voyage days under the trip interruption coverage.

Next-of-kin notification is the flight surgeon's responsibility in an emergency. The vessel's communications system sends a priority message to the emergency contact registered in the passenger's account portal as soon as communication bandwidth allows. Given light delay from the outer system, this notification may take 2 to 3 hours to arrive on Earth. The notification confirms the passenger's status and the vessel's planned course of action; it does not ask for family input into medical decisions, which are made by the flight surgeon and captain.

Passengers are encouraged to ensure their emergency contact information in the account portal is current before departure. The system accepts one primary emergency contact and one secondary. Both should be on Earth or at a location with reliable communications access.
