Metal Forming of Metallic Aircraft Wing Covers: Process Origins, Industrial Development and Programme-Level Evidence

Metallic wing covers are defined here as wing skins plus mechanically attached or integrally machined stringers; an integrally stiffened panel is the monolithic case in which the skin and stiffeners are machined from one plate. This structured narrative review examines upper and lower metallic wing covers as manufacturing objects in civil transport, business-aircraft, and selected military fixed-wing programmes. Aircraft-level evidence is concentrated from 1950 onward, with earlier peen-forming origins included only where they explain later industrial adoption. The evidence base combines peer-reviewed papers, SAE Technical Papers, patents, trade literature, government reports and supplier disclosures, so the review uses explicit source weighting rather than statistical aggregation. Evidence is graded by source strength, and patents are treated as capability evidence rather than proof of production use unless independently corroborated. The synthesis shows that route selection is governed by structural scale, cover role, curvature class, alloy and temper, inherited stock state, panel architecture, and compensation or validation capability. The upper/lower cover divergence that emerges is directly evidenced for selected Airbus, Gulfstream and B-1B cases and is treated, for Boeing and other lineages where cover-separated routes are not publicly disclosed, as a mechanistically supported inference rather than a demonstrated production rule. The strongest public evidence supports peen and particle-impact routes for selected directional or inflected lower-cover cases, Creep Age Forming (CAF) for large smooth heat-treatable covers, and specialised laser or hybrid routes where corroborated by supplier, patent, or named-programme evidence. Modern, non-Western, business-jet, and many military programmes are frequently supported only by patent, supplier, lineage, or contextual evidence and are therefore interpreted cautiously.