Preloaded endovascular delivery systems expand the anatomic eligibility for complex aortic repair by requiring only one iliac access vessel and providing a stable platform for guiding sheaths into challenging target vessels. This article reports the lessons learned and early clinical outcomes using a modified preloaded delivery system for fenestrated endovascular aneurysm repair (FEVAR) in three aortic centers in Europe.From October 2015 to March 2016, consecutive patients presenting with extensive aortic aneurysm treated with a modified preloaded FEVAR were prospectively enrolled from three high volume European aortic centers. The new design is a modification of previous designs of preloaded fenestrated stent grafts and of the p-branch device platform. The technical details of implantation are described and perioperative outcomes, including the learning curve, are collected and reported.All patients (30 patients; 80% men; 70.2 years old) presented for nonurgent repair of either a type Ia endoleak (3/30; 10%), a type I-II-III thoracoabdominal (8/30; 27%), or a type IV thoracoabdominal or pararenal (19/30; 63.%) aneurysm repair of a mean size of 64 ± 13 mm using a custom made device. Primary technical success was achieved in 28 of 30 patients (93%) and assisted primary technical success in 29 of 30 patients (97%). The two technical failures included open conversion to repair a ruptured iliac artery and restenting of a dissected superior mesenteric artery which was recognized hours after the index procedure had finished. The mean procedure time was 277 ± 153 minutes, fluoroscopy time 79 ± 36 minutes, dose area product 112 ± 90 Gy cm2, and contrast volume 87 ± 46 mL. All renal fenestrations were successfully stented without type III endoleak on completion angiogram; the preloaded guiding sheaths were used for 53 of 58 renal arteries (91%). Challenges related to learning to the use of the modified preloaded system were experienced early and had no clinical consequences. Major complications occurred in seven cases (23%), including two perioperative deaths because of stroke and sepsis following primary conversion attributable to iliac rupture. There were no target vessel occlusions or type I/III endoleaks found on postoperative imaging.Based on early experience, the modified preloaded system can be safely and effectively used during FEVAR, with good technical result and a short period of learning. This device expands treatment to patients with compromised iliac access, thus, additional patients and more follow-up will be required to determine unique risks of operating in this patient population.