Inclusion Criteria:
* Have a type B aortic dissection extending to the celiac trunk or beyond
* Are eligible for thoracic endovascular treatment with stent grafts as per local guidelines, and physician's decision
* Have been elected for treatment with commercially available stent graft as per their IFU within 90 days of dissection symptoms onset
Exclusion Criteria:
* General Exclusion Criteria:
* Age \< 18 years
* Pregnant, breast-feeding or planning on becoming pregnant during the entire duration of the study
* Unable to provide written informed consent
* Unable or unwilling to comply with the requirements of the study protocol
* Taking part already in an investigational device or drug study that could interfere with the outcomes being studied
* Active drug addiction or known history of drug abuse within one year of treatment
* Medical Exclusion Criteria:
* Aortic rupture, free or contained including haemothorax, increasing periaortic hematoma, or mediastinal hematoma
* Aortic fistula
* Suspicion of bowel necrosis or irreversible visceral ischemia
* Stage 5 chronic kidney disease
* Life expectancy of less than 2 years due to any other medical condition than the dissection to be treated
* Active malignancy
* Known sensitivities or allergies to the device materials (including cobalt, chromium, nickel)
* Known sensitivities or allergies to contrast materials that cannot be pre-medicated
* Mycotic aortic aneurysm or active systemic infection that may place the patient at increased risk of endovascular infection
* American Society of Anaesthesiologists (ASA) class V (moribund patient not expected to live 24 hours with or without operation)
* Diagnosed or suspected congenital degenerative connective tissue disease (e.g., Marfan's, Loeys-Dietz or Ehlers-Danlos syndrome)
* Uncorrectable coagulopathy, bleeding diathesis or refusal of blood transfusion
* Any major cardiovascular or cerebrovascular ischemic event, including myocardial infarction or stroke, or treatment of such event, within 90 days prior to enrolment
* Any aortic-related interventional or surgical procedure within 30 days prior to enrolment
* Any planned aortic-related interventional or surgical procedure within 30 days after the study procedure
* Anatomical Exclusion Criteria:
* Aneurysmal dilatation of the false lumen defined as maximum transaortic diameter \>55 mm in women or \>60 mm in men in the thoraco-abdominal segment or \>50 mm in women or \>55 mm in men in the abdominal segment, measured inner-wall to inner-wall;
* Inadequate proximal landing zone for the stent graft, such zone being \<20 mm long
* Inadequate proximal landing zone geometry for the Allay® Aortic Stent (e.g. aortic kink)
* Planned implantation of a stent graft with a distal diameter \>38 mm or \<20 mm
* Aorta or iliac anatomy not allowing the advancement of the delivery system
* Subject in whom the thoracic stent graft is either 1) not implanted in its intended position and/or 2) leads to any serious device complication, and/or who has 3) persistent static obstruction of the visceral or both renal arteries, prior to Allay® Aortic Stent implantation, will not be implanted with the Allay® Aortic Stent and will be withdrawn from the study
