Method for manufacturing a sheet 0.5 to 3.3 mm in thickness having an essentially non-recrystallised structure made of aluminium-based alloy wherein, successively a) a molten metal bath is prepared comprising 2.6 to 3.4% by weight of Cu, 0.5 to 1.1% by weight of Li, 0.1 to 0.4% by weight of Ag, 0.2 to 0.8% by weight of Mg, 0.11 to 0.20% by weight of Zr, 0.01 to 0.15% by weight of Ti, optionally at least one element chosen from among Mn, V, Cr, Sc, and Hf, the quantity of the element, if chosen, being from 0.01 to 0.8% by weight for Mn, 0.05 to 0.2% by weight for V, 0.05 to 0.3% by weight for Cr, 0.02 to 0.3% by weight for Sc, 0.05 to 0.5% by weight for Hf, a quantity of Zn less than 0.6% by weight, a quantity of Fe and Si less than or equal to 0.1% by weight each, the remainder being aluminium, and inevitable impurities at a content less than or equal to 0.05% by weight each and 0.15% by weight in total, b) a slab is cast using said molten metal bath c) said slab is homogenised at a temperature between 450°C and 515°C; d) said slab is rolled by hot rolling into a plate having a thickness between 4 and 12 mm; e) said plate is rolled by cold rolling into a sheet having a final thickness between 0.5 and 3.3 mm, the reduction in thickness achieved by cold rolling being between 1 and 3.5 mm; f) a heat treatment is performed during which the sheet reaches for at least thirty minutes a temperature between 300°C and 450°C; g) said sheet undergoes solution heat treated at a temperature between 450°C and 515°C and quenched; h) said sheet is streched in a controlled manner with a permanent deformation set of 0.5 to 5%, the cold working after solution heat treatment being less than 15%; i) artificial ageing is performed comprising heating to a temperature between 130 and 170°C and preferably between 150 and 160°C for 5 to 100 hours and preferably from 10 to 40 hours. a) a molten metal bath is prepared comprising 2.6 to 3.4% by weight of Cu, 0.5 to 1.1% by weight of Li, 0.1 to 0.4% by weight of Ag, 0.2 to 0.8% by weight of Mg, 0.11 to 0.20% by weight of Zr, 0.01 to 0.15% by weight of Ti, optionally at least one element chosen from among Mn, V, Cr, Sc, and Hf, the quantity of the element, if chosen, being from 0.01 to 0.8% by weight for Mn, 0.05 to 0.2% by weight for V, 0.05 to 0.3% by weight for Cr, 0.02 to 0.3% by weight for Sc, 0.05 to 0.5% by weight for Hf, a quantity of Zn less than 0.6% by weight, a quantity of Fe and Si less than or equal to 0.1% by weight each, the remainder being aluminium, and inevitable impurities at a content less than or equal to 0.05% by weight each and 0.15% by weight in total, 2.6 to 3.4% by weight of Cu, 0.5 to 1.1% by weight of Li, 0.1 to 0.4% by weight of Ag, 0.2 to 0.8% by weight of Mg, 0.11 to 0.20% by weight of Zr, 0.01 to 0.15% by weight of Ti, b) a slab is cast using said molten metal bath c) said slab is homogenised at a temperature between 450°C and 515°C; d) said slab is rolled by hot rolling into a plate having a thickness between 4 and 12 mm; e) said plate is rolled by cold rolling into a sheet having a final thickness between 0.5 and 3.3 mm, the reduction in thickness achieved by cold rolling being between 1 and 3.5 mm; f) a heat treatment is performed during which the sheet reaches for at least thirty minutes a temperature between 300°C and 450°C; g) said sheet undergoes solution heat treated at a temperature between 450°C and 515°C and quenched; h) said sheet is streched in a controlled manner with a permanent deformation set of 0.5 to 5%, the cold working after solution heat treatment being less than 15%; i) artificial ageing is performed comprising heating to a temperature between 130 and 170°C and preferably between 150 and 160°C for 5 to 100 hours and preferably from 10 to 40 hours.